If you open Klipper configuration window, then go to "Actions" tab, if you click on "Add action", "Edit Action" or "Advanced", then any left/right click or wheel scroll by mouse on any item on panel or on desktop icons (including contextual menu) is not working at all, only shortcuts can be invoked to interact with desktop.
Can confirm. Probably plasmashell is listed as the parent, and dialogs disable their parent app/window.
*** This bug has been marked as a duplicate of bug 501938 ***