Maybe you are frustrated because it feels as if using the mouse and keyboard instead of a pen feels like a magnitude slower? My designer recently got a graphic

Maybe you are frustrated because it feels as if using the mouse and keyboard instead of a pen feels like a magnitude slower? My designer recently got a graphic tablet and she has got really good at using it. Instead of sketching on a paper, we now sketch on the computer. We save the sketches in Google Drive, so I can easily access them (you could also store them in git...), deleting and copying in the sketches is better than on paper. Plus, the interface you start with is really a blank, white page. Its not really made for this specific use case, but it works surprisingly well! Except for responsiveness (but I am not sure this can be solved automatically), it seems to solve the other 4 problems you mentioned (if exporting to pdf is fine for you).