Hi @NKKKY, thank you for your proposal. Please don’t remove the template. It’s ok if you don’t feel like filing it now. Others may jump and help as well. We are trying to set up a process common to all proposals (see the link in the template itself).
Also note that you are encouraged, and even expected, to vote your own proposals.
Is there a DAW that allows to switch x/y? I can see how one can work with each configuration, but from the DAW developers point of view, allowing users to switch looks like a nightmare (to me, and I’m not a developer) because there are so elements in the UI that need to change their axis too (i.e. expressions or automation lines).
It’s simply because when I am nodding my head I would like to have a vertical visualization to be in sync! 
for the vibe. - it’s not that hard to accomplish.
The reference for this request are tracker interfaces, but they are very different from a piano roll. There is not even a “piano”, or maybe I didn’t look well enough.
Renoise is mentioned as an example. See Tracker Interface - Renoise User Manual
Are there any DAWs offering the possibility to switch axis of the piano roll, or that come with the piano roll in the horizontal axis?
I don’t want to argue against this request, which is valid in its own. I just want to improve the description to make a good case. I suspect offering this change of axis implies a major development undertaking.
I am just fine if it’s just vertical. Doesn’t need to be a whole new interface concept like a Tracker Interface.