The old version of windows pencil2D I have used for several months now.
As you know the program crashes as it has memory problems, it does not release the used memory and eventually crashes. This happens with copy / pasting parts of an animation and then moving it. This happens a lot with version 0.5.4. So after copy and paste a few things I start saving and backup it. If you see pieces of animation going away like magic, that is an indication that pencil2d is about to crash.
My suggestion for the new program would be:
I would add an option to choose between “keep every frame in the RAM” or “save as much as possible to disk, and cache X frames before and after the animation”. This will keep the memory usage very low and still make the program fast enough.