I have been using ASP for some time now, along with other art apps, like procreate, infinite painter, concepts, affinity etc. ASP is probably the closest to a complete art app for me, but somethings in other apps have a nicer implementation, which i think could improve ASP.
1. with the introduction of the full screen mode in the beta, i don‘t see much use for the painting mode. For my workflow i would either use the full ui, as i need selection and fill tools, and frequently go through the top menu for commands. When i want to concentrate on drawing only i would use the fullscreen mode, and switch back when i want to change tools or do other operations. The drawing mode offers not enough benefits to me to use it, it has too much UI for concentrated drawing, and too little for the rest. It would clean the UI too, if there would be only 2 modes. Perhaps a prefernces setting for the parts of the UI one wants to hide, like the one in the original AS, would be useful.
2. some more use of gestures could benefit the full screen mode. Infinite painter has the 3 finger swipe to the top or bottom to resize the brush, and left/right for opacity (or flow in ASP). This is quite elegant and works well.
A single finger swipe or swipe out gesture to expand or hide a palette could also be useful. Infinite painter has the minimal layers menu on the right, which can be expanding by swiping. I find this quite intuitive.
3. the color option would make more sense to me as it was in the original AS, at the top of the color bar, but not scrolling (like the favorite tools in the left tools bar)
4. i would like to see a permanent layers menu at the right, perhaps as a switch with the colors like the one you implemented in the latest beta between opacity/size sliders and colors. Expanding it could be done by swiping.
These are just some ideas. I think ASP already has great features, but a slightly cleaner and more logical UI would help improve even more.
Thanks for the work, i hope you can use my feedback!