Subject says it all. I open up an app in Plasma, try to minimize it with the left button and it seems to just nuke the app and window. If it is minimizing it, I can't figure out how to bring it back. There doesn't seem to be a taskbar on either panel I set up.
Never mind; there was something wrong with both of the panels I had installed. When I created a new one, the task bar was on it along with all of those minimized windows.
Started and solved your own support ticket. Very good :-)