Reproduction steps:
1. Open the attached “UIScrollbar.zip” project
2 Open the UI Builder window (Window > UI Toolkit > UI Builder)
3. Select the “text.uxml” from the Hierarchy
4. In the Inspector check the “Editor Extension Authoring” checkbox
5. Move the scrollbar in the Library panel

Expected result: The scrollbar moves
Actual result: The scrollbar is unresponsive

Reproducible with: 2023.3.0b9, 6000.0.2f1
Not reproducible with: 2021.3.38f1, 2022.3.29f1, 2023.3.0b8

Reproducible on: Windows 11
Not reproducible on: No other environment tested

Workaround: Resizing the whole panel on the left makes the scrollbar responsive again

Note:
- The issue also re-appears when the “Editor Extension Authoring” option gets unchecked