3.8.2

* More natural appearance of the theme "Proton" matching to Firefox's Proton theme.
* The new tab button is now draggable as a link to the URI `about:newtab`, with the Shift key. This means that you can open a new tab at arbitrary position in the sidebar via drag and drop.
* Add icons to the new tab action selector panel for better user experience.
* Accessible labels of faviconized tabs from screen readers and voice recognition systems.
* Allow to open `about:newtab` links dropped in the sidebar.
* Show confirmation dialogs in the sidebar more safely even if they are triggered by quick actions.
* Never open new tab by middle click on confirmation dialogs shown in the sidebar.
* Never show invalid "undefined" item in the list of other devices.
* Apply the height of the user style editor immediately when a different value is imported.
* Open new blank tab as a child correctly, even if the insertion position is configured as "no control" or "next to the recently opened".
* Re-introduce an option to change the color of the toolbar icon, for better accessibility.
* Don't clear drop position marker while dragging, on Linux environment.
* Save changed config of the new tab insertion position via the right click menu on the toolbar button correctly.
* Try applying the background color to the sidebar ASAP.
* Allow to toggle muted state of tabs even if it is not sound-playing (if the mute button is shown forced by custom user styles).
* Subpanel contents now have its owner window's ID as the `windowId` URL parameter, [by NiklasGollenstede](https://github.com/piroor/treestyletab/pull/2899). Thanks!
* Subpanel is now restricted to a page contained in the provider extension itself, [by NiklasGollenstede](https://github.com/piroor/treestyletab/pull/2898). Thanks!
* API improvement: Add ability to handle and override events on the new tab button via [notification messages with types `new-tab-button-mousedown`, `new-tab-button-mouseup` and `new-tab-button-clicked`](https://github.com/piroor/treestyletab/wiki/API-for-other-addons#when-the-new-tab-button-is-clicked).
* API improvement: Add ability to control extra contents in the new tab button via [messages with types `set-extra-new-tab-button-contents` and `clear-extra-new-tab-button-contents`](https://github.com/piroor/treestyletab/wiki/Extra-Tab-Contents-API#extra-contents-in-the-new-tab-button).
* API behavior change: [`tab-clicked` type message](https://github.com/piroor/treestyletab/wiki/API-for-other-addons#when-a-tab-is-clicked) is now delivered only when both `tab-mousedown` and `tab-mouseup` are not canceled.
* Update `de` locale by [SammysHP](https://github.com/SammysHP). Thanks!
* Update `ko` locale by [BoredSomeone](https://github.com/BoredSomeone). Thanks!

3.8.1

* Prevent inifinite toggling of the sidebar scrollbar on macOS, when there are enough number of tabs which triggers overflowing. The fix was unexpectedly lost on the released version 3.8.0.
* Update `ru` locale by [wvxwxvw](https://github.com/wvxwxvw). Thanks!

3.8.0

* Restructure behaviors about closing and moving of a parent tab.
  * In the sidebar, now there are some permanently fixed behaviors and some configurable presets:
    * Closing a parent tab with collapsed tree: closes the entire tree.
    * Moving a parent tab with collapsed tree: moves the entire tree.
    * Moving a parent tab with expanded tree: behaves according to configurations under the section "Drag and Drop".
  * There is a preset for people using Firefox's native tab bar as an UI to operate solo tab. In this case all tab operations done outside of the sidebar (Firefox's native tab bar, keyboard shortcuts, or other addons) are treated as operations for solo tabs, not tree of tabs.
  * There is a preset for people desireing TST to control tabs as trees always. In this case all tab operations are treated same as operations in the sidebar, even if it is done on Firefox's native tab bar, keyboard shortcuts, or other addons.
  * Otherwise you can configure behaviors for each case: closing of a parent with expanded tree in the sidebar, closing of a parent with collapsed/expanded tree outside of the sidebar, moving of a parent with collapsed/expanded tree outside of the sidebar, and more options for cases with closed sidebar.
* Better accessibility information for the sidebar. This change should help [controlling of the sidebar via speech recognition](https://github.com/piroor/treestyletab/wiki/How-to-control-Tree-Style-Tab-via-speech-recognition).
* Add the simulated "New Tab" context menu command on tabs.
* "Close Tabs to the Bottom" and "Close Other Tabs" context menu commands now skips collapsed descendants of the context tab.
* Open tabs from a bookmark folder with correct order. (This looks to be a regression on recent versions.)
* Prevent inifinite toggling of the sidebar scrollbar on macOS, when there are enough number of tabs which triggers overflowing.
* On macOS, in-tab padding is correctly applied avoiding the scrollbar covers clickable UIs. (It was applied to wrong side.)
* Proton theme: Show container identifier line at top of pinned tabs.
* Proton theme: Remove separator border between pinned tabs and regular tabs.
* Apply the icon color or the text color defined by the active theme to TST's toolbar button icon, context menu icon, and the sidebar panel switcher.
* Rebuild sidebar contents more certainly when mis-synchronization between the main process and the sidebar contents is detected.
* Becomes to more robust around tabs reopened immediately by other addons like Temporary Containers.
* Becomes to more robust around closing/moving of parent tabs as solo tabs.
* Don't show needless "Send Tab to Device" simulated context menu item in the context menu on non-tab area.
* Open duplicated tabs based on the configuration more correctly.
* Expose an expert option UI to control the number of scroll lines for keyboard shortcuts.
* The height of the subpanel is now saved and restored for each provider addon.
* Better appearance for the subpanel switcher: more easily recognized as a switcher UI.
* Accept icon images with non 16px size for the subpanel switcher.
* API improvement: now you can specify [`initialHeight` or `fixedHeight` for your subpanel](https://github.com/piroor/treestyletab/wiki/SubPanel-API#how-to-register-a-subpanel).
* API improvement: [custom state of tabs](https://github.com/piroor/treestyletab/wiki/API-for-other-addons#apis-to-set-custom-state-for-tabs) are added/removed safely even if they are given as any type value not a string.
* API improvement: Support CSS length `delta` and `position` parameters for the [`scroll` API](https://github.com/piroor/treestyletab/wiki/API-for-other-addons#scroll-the-tab-bar).
* API improvement: Support `duration` parameter for the [`scroll` API](https://github.com/piroor/treestyletab/wiki/API-for-other-addons#scroll-the-tab-bar).
* API improvement: Add new API [`stop-scroll`](https://github.com/piroor/treestyletab/wiki/API-for-other-addons#scroll-the-tab-bar) to cancel in-progress scroll animations.
* Update `ru` locale by [wvxwxvw](https://github.com/wvxwxvw). Thanks!

3.7.4

* Add a theme like [Proton](https://www.omgubuntu.co.uk/2021/02/try-firefox-proton-redesign-ubuntu) experimentally. Proton is the next UI theme of Firefox itself.
* Rename the theme "Plain" to "Photon". Photon is the current UI theme of Firefox itself.
* Restructure tab context menu items to match to the one on Nightly 89.0a1.
* Add a new expert option to close a parent tab as a solo tab by triggers outside of TST, even if it has collapsed children, with visible sidebar.
* Increase the maximum size of the user styles about 12KB.
* Add a [debug option to configure the delay to detect duplicated tabs](https://github.com/piroor/treestyletab/issues/2845).
* API improvement: introduce [`create` which creates a new tab bypassing TST's tab position control behaviors](https://github.com/piroor/treestyletab/wiki/API-for-other-addons#open-new-tab-bypassing-tsts-tab-control-behavior).
* Update `ru` locale by [wvxwxvw](https://github.com/wvxwxvw). Thanks!

3.7.3

* Add support for Firefox 88+ compatible "Close Tabs to the Left (Top)" context menu command.
* Prevent the cached helper addon IDs to be synchronized via Firefox Sync. This should solve problems around initialization of helper addons after TST is updated dynamically.
* Don't apply "Tabs from any other trigger" option for new tabs opened from TST's new tab button and the new tab action menu.
* Show tab drag feedback images at bottom-right of the cursor like Firefox does, for better visibility of drop targets.
* Update `ru` locale by [wvxwxvw](https://github.com/wvxwxvw). Thanks!

3.7.2

* Limit maximum rows of pinned tabs (50% height of the sidebar by default) and allow to scroll pinned tab rows with the wheel.
* Keep tree structure more robustly for tabs immediately closed and reopened with different contaienr by any other addon.
* Don't restore closed tabs doubledly on a restoration with Ctrl-Shift-T.
* Restore root level tabs to their original position correctly, even if "new tabs from any other trigger" option is changed. (regression on recent versions)
* Clean up only dummy group tabs even if "Close descendants too" is chosen for options under the "When a parent tab is closed or moved just as a solo tab" => "Custom" section.
* Apply "When a parent tab is closed or moved just as a solo tab" => "Recommended behavior for people who still use the native tab bar of Firefox itself also" => "Replace closed parent with a dummy tab and keep the tree" behavior correctly. (regression on recent versions)
* Show confirmation for closing descendants when a collapsed tree is closed via keyboard shortcuts. (regression on recent versions)
* Move detached descendants after all other existing descendants automatically, to keep correct tree structure. (regression on recent versions)
* Add an expert option to change acceptable accelerator key to match the one on Firefox itself modified via `ui.key.accelKey`.

3.7.1

* Consistent the position of the new tab action selector button in both regular and private windows.
* Update `ru` locale by [wvxwxvw](https://github.com/wvxwxvw). Thanks!

3.7.0

* Show in-tab container indicators (colored bars) with a styling more similar to Firefox's native one.
* Introduce syntax highlighing in the user styles editor (based on the [CodeMirror](https://codemirror.net/).)
* Remember the height of the user styles editor.
* Cancel the visual gap of tabs produced with dynamically showing/hiding toolbars only when it is triggered by mouse operations on the sidebar in regular windows (not fullscreen mode), by default.
* Add a new expert option to control how tabs to be opened for any other cases not covered by existing options.
* Deactivate "Reopen in Container" and other container tab related features for private windows, like as Firefox itself does.
* API improvement: introduce [`*-of-<id>` suffixed keywords to get tabs based on relations from any arbitrary tab](https://github.com/piroor/treestyletab/wiki/API-for-other-addons#basics-to-specify-tabs).
* API improvement: introduce [`lastDescendant` keyword to get tabs based on tree structures](https://github.com/piroor/treestyletab/wiki/API-for-other-addons#basics-to-specify-tabs).
* Update `ru` locale by [wvxwxvw](https://github.com/wvxwxvw). Thanks!
* Update `de` locale by [SammysHP](https://github.com/SammysHP). Thanks!

3.6.5

* Show favicons same to Firefox's built-in for `about:logins`, `about:profiling`, `about:protections` and `about:robots` tabs.
* Detect tabs opened from external applications correctly. (The detection result was wrong: only new tabs opened with `openerTabId` while all Firefox windows were inactive were detected as "opened by external applications".)
* Don't show not-initialized-yet menu elements while the startup process.
* Update `ru` locale by [wvxwxvw](https://github.com/wvxwxvw). Thanks!

3.6.4

* Prevent to mis-shift the sidebar content with regular tabs, non-fullscreen windows placed at coordinates like (*, 0).
* Expose an expert option to deactivate shifting of the sidebar contents with temporarily shown toolbars.
* Fix incompatibility with [Tree Style Tab Mouse Wheel](https://addons.mozilla.org/firefox/addon/tree-style-tab-mouse-wheel/) on Firefox 84 and later. ([Thanks to @MISONLN41!](https://github.com/piroor/treestyletab/pull/2784))
* Ensure moved active tab visible even if it is moved via keyboard shortcuts Ctrl-Shift-PageUp/PageDown.
* Turn moved active tab visible even if it is moved from an collapsed tree to the top level via keyboard shortcuts.
* Hide the dummy tab behind the background carten completely.
* Provide custom properties for theme colors with different opacity, with a numeric suffix like `-10` per 10%. For example `--theme-colors-tab_background_text-30` means "the color ame to `tab_background_text` but 30% opacity".
* Update `ru` locale by [wvxwxvw](https://github.com/wvxwxvw). Thanks!