When I work from home, I routinely run krdc fullscreen on desktop 2.  Then to do other local Linux tasks, I switch back to desktop 1.

On KDE4, I used to be able to return to krdc on desktop 2 by clicking it on the taskbar, but in KDE5 it seems that fullscreen windows are removed from the taskbar (and they reappear on the taskbar when you exit fullscreen mode).  In fact, because I have a 'taskbar launcher' set up for krdc, if I click that, I get a second instance of krdc.

In any case, I don't see a reason to remove a fullscreen window from the taskbar - the task is still active...

I'm running Linux Mint 18.1 KDE - don't know what exact version of KDE that is.  I used to get the version from Dolphin's 'Help - About KDE' dialog, but it's not displayed there any more.