PSA: Disable the UI editor by going to:
%localappdata%\Roblox\Versions\version-17545b00677240ae\BuiltInPlugins
(you may need to find the correct version- folder if Roblox updates after this post)
And deleting: UIEditor.rbxmx from the BuiltInPlugins folder.
The UI editor tab will still show up, but it won’t hijack your workflow, display any handles or sink mouse events. Class changer plugins also work now.