[Feature requests] repair the onion screen

[bongblender]

why it's showing the previous frame in full color under the current frame, it's not working as an onion screen should work.
also, there is no setting for onion layer count.
raster or SVG, every animation software has to have a good onion screen feature.
Please work on this problem as soon as possible.
this software has a bright future. i like it very much, but I NEED THE ONION SCREEN.
make it like pencil2D onion screen if possible.
Thank you.