08-09-2022, 10:57 PM
A 200Mpx, any layer is 1.2GB, so the undo stack grows fast since it just makes copies of layers. You can tweak Edit ➤ Preferences ➤ System resources to reduce the minimum amount of undo levels. You can also reduce the tile cache size to make sure Gimp fits in your RAM (but it can become very slow instead.)