CanvasPainter has an undo function that allows 35 undo levels on the desktop and 15 levels on mobile devices.
The Undo methodology that CanvasPainter employs is one where the undo steps are held in memory. If you would like to save your Canvas at anytime you will need to click/tap on the Save button.
Tip: CanvasPainter only saves Canvases that you tell it to save. Be sure to save your progress!