I have a specific app configured to open in Desktop 2. I have the task manager configured to show only tasks from each desktop.

The app correctly opens in Desktop 2 but the window manager always changes the focus to Desktop 2. I don't want that. I want the app to run quietly in the background.

I changed the focus stealing level to something other than None. That sort of works in that the window manager does not change to Desktop 2, but the window manager also creates a task manager icon in the Desktop 1 task bar that annoyingly flashes a few times. As I have the task manager set to display tasks only from the current desktop, I don't know why the icon appears on Desktop 1.

The task icon text is also weirdly drop-shadowed.

When I select Desktop 2 and then return to Desktop 1 the task manager icon does not disappear from the Desktop 1 task bar.

I want to open the app in Desktop 2, no task bar icon to appear in Desktop 1, no flashing in Desktop 1, and no focus stealing. Just run quietly in the background in Desktop 2.

I am not using Activities or Screen. Very generic.

Any idea how to fix this?

Thanks.

Is this a regular application or a custom / proprietary one? Just to know if it plays "nice" or not with the workspace. On the same league, do you see the same effect with other applications?

I tried some other apps, such as LibreOffice and some native KDE apps. Same results. Either the focus changes or the nagging task bar icon in Desktop 1 appears.

The particular app that started this thread is VirtualBox. I prefer my virtual systems to open in Desktop 2. I don't run them 24/7 but I use them often. Probably half the time I want to start working in them immediately and then the changing of focus is acceptable. Yet other times I want to start the virtual machines in the background because I'm not ready to start working immediately. Then the forced focus change is disruptive. I'd rather stay with never having the focus change because the virtual machine is only a one step Ctrl-F2 to access. When the forced focus change interrupts my immediate concentration then I need two steps to return to Desktop 1 because I have to escape the internal focus of the machine before I can press Ctrl-F1.

Yet as I mentioned, preventing the focus stealing means I'm interrupted with the flashing task bar icon in Desktop 1 with the weird drop shadow fonts.

I disabled launch feedback for the virtual machines but the task bar icon still flashes in Desktop 1.

I probably would better tolerate the flashing task bar icon in Desktop 1 if those weird drop shadow fonts weren't used. The flashing is temporary but for whatever reason, the drop shadow effect distracts me a great deal. Is there a way to stop the drop shadow effect?

Focus stealing prevention and the currently active virtual desktop is the domain of the window manager, KWin. I've moved this to the KWin forum.

If you start a normal application (say KWrite or Kate for instance) with these sort of settings applied, is the virtual desktop changed?

Probably not really a WM issue.
KWin blocks the focus request of the client and marks it urgent instead - what usually will cause the flashing icon.
Once the window got activated, the urgency should be withdrawn ("xwininfo -wm" to check)

What the taskbar makes out of the urgency hint is the taskbars thing
If the urgency flag is not withdrawn, please file a bug against kwin.