when at horizontal bottom screen, icon task list in a pocillo themed panel shows underlining for running app’s, in minimized windows.
( if size of panel is big enough, though ).
If set to vertical left side of screen, there is no way to see those underlining. Some other themes provide underlining for running app’s ( arc… ) but seem to produce weird behavior with size/height of panel so I stay with pocillo - which is very beautiful anyway
Ubuntu-budgie 18.04, by the way.