OK button to enter pattern

[XORadmin]

That sounds actually like a good thing to do and i will consider it to think about it and research possible side effects.

Awesome!

Undo can totally change all your sequences, depending on what you did before. Just imagine you hade a intense copy paste session. Then play the sequences and then you place some old sequence arrangement by using undo. I can think of everything like notes that keep playing etc. And of course the issue that it causes problems when a empty sequencer field is playing, because it has just been removed by undo or any other copy pase or delete actions.

Ahh yeah I see what you mean. I guess I can't help but compare everything to Ableton Live (which can undo while playing), but that is obviously a more heavy program with endless resources, memory etc.

Oh no....i never used ableton, so i don't know what you are talking about.
But comparison is here definitely out of proportion. Indeed gigaherz computers with big screens and endless memory and a full development-team vs. Megahertz microcontroller with a mini low-res screen, only kilobytes of memory and a 1 person development team who also has to arrange everything else in his mini company :-)