[SOLVED] Weird behaviour of task manager in KDE on Bullseye

[closedbox]

I recently installed Debian Bullseye with KDE Plasma. I have noticed a strange problem with the "Icons-only-taskmanager" which is located on the taskbar. The problem arises if I have launched two (or more) programs, say Firefox and Dolphin. Suppose I am viewing Firefox and click on "Show Desktop" to display the Desktop. If I then click on the icon for Dolphin in the task manager, the Firefox window (rather than Dolphin) is displayed. In fact, after clicking "Show Desktop", regardless of which icon I click on afterwards, the window which I was viewing before clicking on "Show Desktop" will pop up again. The only exception is if the program wasn't already running. In that case its window pops up just as expected, but beneath it also the window of the previously viewed application is displayed.

Has anyone else experienced this problem, and is there any way to fix it?

KDE Plasma Version: 5.20.5
KDE Frameworks Version: 5.78.0
Qt Version: 5.15.2
Kernel Version: 5.10.0-5-amd64

I haven't really done much customization of the desktop environment, so I don't think I've managed to break anything on my own.

[NFT5]

The problem is not with Task Manager, rather it is the way that the "Show Desktop" icon works. What you'd expect is that it minimises all open windows, leaving the desktop visible, but it doesn't. What it actually does is to bring the desktop to the top of the stack, leaving other windows in their previous state, underneath. Thus, when you click on an icon you actually minimise that window with the first click and restore it with the second. To get the action that you expect, try minimising all windows individually and then click on one of the icons. The window will be restored.

[closedbox]

Thanks for your reply!
Understanding exactly what went wrong allowed me to find a solution. There is a KWin script called "MinimizeAll" which minimizes all windows. It can be added to the task bar as a widget, and it is also possible to add a keyboard shortcut for it in the settings. Now everything works as it should.

I really wonder why such a strange "Show Desktop" widget is included as default, when on every other DE (that I've tried at least) the default is to minimize all windows.