I use an autohidden panel at the bottom of the screen which contains an application starter, lock / logout buttons and the calendar and clock widget. (See screenshot.) After switching to Plasma 5.5.4, I could not get this panel to hide any more. I also switched it a few times between "display always" and "auto hide" and moved it to different borders of the screen to no avail. Another autohidden panel I had in the top-left corner of my screen still worked fine. I ended up recreating my panel and removing the original one - the new panel will correctly autohide, as expected. Thus maybe this report is pointless, but I just wanted you to know in case you may have an idea what could have caused this and it can be fixed for other users. Reproducible: Always
Created attachment 97310 [details] Screenshot showing the panel at the bottom border which is reluctant to auto-hide.
Can you run "xprop" and click on the panel please.
Unfortunately I cannot - as stated above, I already recreated the panel (which now works as desired) and discarded the original one. :-( Maybe I should have waited for a reply hier for a few days, I honestly I didn't expect such a quick response and thus just tried to get it working again as quickly as possible...
As stated above, I currently do not know what additional info I could provide.
Have you encountered this bug later/currently?
5.5 is super old with no newer reports. closing.