When an applet is moved in the area, usually covered by a currently hidden auto-hide panel, the applet will get "sucked" into the panel. So it looks like the logic for moving applets from the desktop containment into a panel doesn't cover the use-case of a panel being hidden. Running P5/KF5 from git master + Qt 5.5.1
Looks like this is already described in #351217 - but as #351217 mixes several different issues, I'll keep this one here open instead of closing it as a DUP to have a single-issue-bug.
Confirming this bug in: Distribution: KDE neon Developer Edition Unstable Branches KDE Plasma Version: 5.10.90 KDE Frameworks Version: 5.37.0 Qt Version: 5.9.1 Kernel Version: 4.10.0-32-generic Maybe panel could be shown in settings mode upon dragging of a widget - to point exact target place for dropping widget.
Yep, confirmed. Very unusual.
This appears to be fixed as of today's git master (which will become Plasma 6.5), if not earlier.