I wasn't able to find the exact place, but it's not a huge issue. I'm curious: How many people are working on Ourpaint? Is this a solo project? It's very impressive! I'd use it as a main tool if it had the ability to select and move bits of an artwork.
Hi! Our Paint is entirely developed by me (1 person).
The selection+move feature is intentionally left not implemented because you won’t be able to do it on paper traditionally. This forces you to draw it well or redraw and after a while you shouldn’t need to rely on selection/move/transform to adjust your drawings :)
The fixed move tool (by 1000px increment) is gonna be available in the next version :D