diff --git a/src/main.ts b/src/main.ts
index 6548e11..70c1c36 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -47,6 +47,7 @@ interface ReadwisePluginSettings {
   booksToRefresh: Array<string>;
   booksIDsMap: { [key: string]: string; };
   reimportShowConfirmation: boolean;
+  frontmatterBookIdKey?: string;
 }
 
 // define our initial settings
@@ -65,6 +66,114 @@ const DEFAULT_SETTINGS: ReadwisePluginSettings = {
   reimportShowConfirmation: true,
 };
 
+class AdvancedModal extends Modal {
+  plugin: ReadwisePlugin;
+
+  constructor(app: App, plugin: ReadwisePlugin) {
+    super(app);
+    this.plugin = plugin;
+  }
+
+  /** helper to extract all book IDs from frontmatter in the readwiseDir ("base folder"),
+  perfectly matching them to the document they came from */
+  async extractBookIDs() {
+    console.log('Readwise Official plugin: extracting book IDs from frontmatter...');
+    const files = this.plugin.app.vault.getMarkdownFiles();
+    const bookIDs: { [bookID: string]: string } = {};
+    for (const file of files) {
+      if (file.path.startsWith(this.plugin.settings.readwiseDir)) {
+        const cache = this.app.metadataCache.getFileCache(file);
+        // skip if there's no cache
+        if (!cache) continue;
+
+        const frontmatter = cache.frontmatter;
+        // skip if there's no frontmatter
+        if (!frontmatter) continue;
+
+        const bookID = frontmatter[this.plugin.settings.frontmatterBookIdKey];
+        if (bookID) bookIDs[file.path] = bookID;
+      }
+    }
+
+    return bookIDs;
+  }
+
+  onOpen() {
+    const { titleEl, contentEl } = this;
+
+    titleEl.setText('Advanced settings');
+
+    // add new setting that allows text input
+    new Setting(contentEl)
+      .setName('Book ID frontmatter key')
+      .setDesc('The frontmatter key used to store the Readwise book_id. If set, will be used to identify the export for syncs.')
+      .addText(text => text
+        .setPlaceholder('readwise-book-id')
+        .setValue(this.plugin.settings.frontmatterBookIdKey)
+        .onChange(async value => {
+          console.log('Readwise Official plugin: setting frontmatter book ID key to', value);
+          this.plugin.settings.frontmatterBookIdKey = value;
+          this.plugin.saveSettings();
+
+          // enable/disable populate button depending on whether the key is set
+          const populateButton = contentEl.querySelector('.rw-setting-populate-book-id');
+          if (populateButton instanceof HTMLButtonElement) {
+            populateButton.disabled = !value;
+          }
+        }));
+
+    // button to populate the frontmatter with using
+    // the frontmatterBookIdKey and matching it
+    // with whatever's saved in booksIDsMap
+    return new Setting(contentEl)
+      .setName('Populate frontmatter key')
+      .setDesc('If the book ID frontmatter key is configured above, this will populate the frontmatter key setting with the first key found in the booksIDsMap. This will not overwrite existing keys.')
+      .addButton(button => button
+        .setButtonText('Populate')
+        .setClass('rw-setting-populate-book-id')
+        .setDisabled(!this.plugin.settings.frontmatterBookIdKey)
+        .onClick(async () => {
+          this.plugin.notice("Populating frontmatter with book IDs...", true);
+          console.log(`Readwise Official plugin: populating frontmatter key ${this.plugin.settings.frontmatterBookIdKey} with matching value from booksIDsMap...`);
+
+          const readwiseExports = this.plugin.app.vault.getMarkdownFiles();
+          for (const file of readwiseExports) {
+            console.log('Readwise Official plugin: checking file for frontmatter', file.path);
+
+            const cache = this.app.metadataCache.getFileCache(file);
+            if (!cache) continue;
+
+            const frontmatter = cache.frontmatter;
+            if (!frontmatter) continue;
+
+            const existingBookId = frontmatter[this.plugin.settings.frontmatterBookIdKey];
+            if (existingBookId) continue;
+
+            const bookId = this.plugin.settings.booksIDsMap[file.path];
+            if (!bookId) continue;
+
+            // set the book ID in the frontmatter
+            await this.app.fileManager.processFrontMatter(file, frontmatter => {
+              // only set if it's not already set 
+              const keyAlreadySet = frontmatter[this.plugin.settings.frontmatterBookIdKey];
+              if (!keyAlreadySet) {
+                console.log(`Readwise Official plugin: setting frontmatter key for "${file.path}" to ${bookId}`);
+                frontmatter[this.plugin.settings.frontmatterBookIdKey] = bookId;
+              }
+            })
+          }
+
+          this.plugin.notice("Frontmatter populated with book IDs", true);
+        })
+      );
+  }
+
+  onClose() {
+    const { contentEl } = this;
+    contentEl.empty();
+  }
+}
+
 export default class ReadwisePlugin extends Plugin {
   settings: ReadwisePluginSettings;
   fs: DataAdapter;
@@ -732,6 +841,17 @@ class ReadwiseSettingTab extends PluginSettingTab {
           }
         );
 
+        new Setting(containerEl)
+          .setName('Advanced settings')
+          .setDesc('Customize additional settings for the Readwise plugin')
+          .addButton(button => {
+            button
+              .setButtonText('Open')
+              .onClick(() => {
+                new AdvancedModal(this.app, this.plugin).open();
+              });
+          });
+
       if (this.plugin.settings.lastSyncFailed) {
         this.plugin.showInfoStatus(containerEl.find(".rw-setting-sync .rw-info-container").parentElement, "Last sync failed", "rw-error");
       }