Scheduler: add a note to scrolling.mode (DevExpress#6824)

api-reference/_hidden/dxSchedulerScrolling/mode.md

@@ -16,4 +16,10 @@ All appointments are simultaneously loaded into the DOM, and the whole grid is r
 - **Virtual**          
 Appointments are loaded into the DOM when they get into the viewport and are then removed once they leave it; the grid is rendered within the current viewport only. [View Demo](https://js.devexpress.com/Demos/WidgetsGallery/Demo/Scheduler/VirtualScrolling/).
 
-[note] Virtual mode is available for all [views](/api-reference/10%20UI%20Components/dxScheduler/1%20Configuration/views '/Documentation/ApiReference/UI_Components/dxScheduler/Configuration/views/') except *"agenda"*.
+[note]
+
+- Virtual mode is available for all [views](/api-reference/10%20UI%20Components/dxScheduler/1%20Configuration/views '/Documentation/ApiReference/UI_Components/dxScheduler/Configuration/views/') except *"agenda"*.
+
+- Specify the component's [height](/Documentation/ApiReference/UI_Components/dxScheduler/Configuration/#height) if you use virtual scrolling. Do not use relative units for height (it prevents Scheduler from maintaining fixed dimensions for virtual scrolling to work correctly).
+
+[/note]