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I've been hacking my way around using the cut brush and flipping the stamp to achieve a mirrored drawing,
but It's really quite a chore to do because sometimes I must do this multiple times if I need to make changes to the drawing....
I've attatched a video of krita's implementation that I think is quite user friendly, and it even allows for snapping to the center x and y positions of the canvas.
I can imagine a feature like this comfortably sitting in the guideline panel if you guys were able to implement this..

I just assigned keystrokes to "duplicate layer" and "flip image". Good enough for now, but some real kaleidoscope implementation for drawing would be nice.