The overlays in FolderView (select, deselect, "open cascading folder popup") are just circles and not easily recognized as such (user testing showed). They are also inconsistent with Dolphin which uses plus/minus icons for that. This icons in action-overlays.svgz in "widgets" of Plasma's Breeze theme should be changed to more recognizable ones.
Kai, do you have some images to show this behavior?
Created attachment 103962 [details] Dolphin overlay vs Plasma FolderView
Git commit badf8acfe2c07adb7be5a1cbb01401651e5ca25e by Kai Uwe Broulik. Committed on 06/03/2017 at 13:26. Pushed by broulik into branch 'master'. [Breeze Plasma Theme] Improve action-overlay icons The current ones aren't really descriptive and vastly different from what Dolphin uses. Differential Revision: https://phabricator.kde.org/D4917 M +- -- src/desktoptheme/breeze/widgets/action-overlays.svgz https://commits.kde.org/plasma-framework/badf8acfe2c07adb7be5a1cbb01401651e5ca25e