I though this wasn’t possible and almost gave up on Logic over this. I couldn’t find anything about it – neither in the manual nor in the settings, but now I stumbled upon it in some Youtube video… What a pleasant surprise!
This is how it’s done: click and drag the bottom-left corner of the track-title. Simple, I know – I tried dragging the bottom of that area about 50 times with all imaginable key-combinations pressed at the same time… well… now I know…
The technical term seems to be “Individual track zoom” and the cool thing is that if you now change the track heights globally through the little slider on the bottom-right of the window, it all scales relatively – and up/down to a certain max/min
