I’m trying to start Plexamp in full-screen mode automatically when I start Plexamp.
It used to be possible that when you closed Plexamp while in full-screen mode, it also would startup again in full-screen mode. It would remember the screen size on exit. This does not seem to be the case anymore.
Plexamp doesn’t have a full-screen mode, AFAIK.
You can maximize its window, which won’t cover the task bar on Windows.
On Windows, you simply edit the shortcut to Plexamp and set it to start “maximized”.