This is very nice project and who I am to judge, I don't even have the console, but... I made a tracker in even worse conditions regarding screen resolution so I have a tiny bit of knowledge (?) Anyway, feel free to ignore my grumbling.
-
Get yourself nice 5*8 pixels font, this one hurts my eyes. I can draw you one if you want.
-
When drawing pattern editor, don't draw the cells for each pattern row, just make a 1 px verticsl spacing. Vertical lines between channels are ok btw. This would allow to place more rows on the screen at the same time which makes using the tracker much easier.
-
Use 3*5 px tiny font for the places where you want to save even more screen space. I have an almost finished one, only numbers and uppercase letters though. You can check u8g2 library fonts, there should be some suitable ones for any pixel dimensions.
-
I don't know what are the <0>... things on the left in note editor, but they also seem to waste some space. These are pattern selectors?
-
BPM number is misleading for hardcore tracker enjoyers, you may place speed (how many ticks per pattern row) and rate (how many ticks per second, idk if in your tracker you can change this parameter) settings. You can still leave BPM counter but only as an informational one.
-
Make a bottom line where one long line of text would be. Print some tips and hints there depending on where the user's "cursor" is. This would help newbies to get used to your tracker.
-
Is this me or your tracker runs in halve the resolution? It's your business of course but you could place a lot more on the screen if in full resolution. Maybe a switch in settings so people with good vision could use the full screen resolution?
Okay that's all... And hey, I wanted to be the first for the tracker, but you were faster! Anyway, good luck, looks like my tracker isn't really possible on Playdate because there is no way to directly control the hardware, I am afraid 