As you can see, the status bar in the map editor is pretty empty.

What I propose is to put there x/y of map tile that is under cursor. This would save lot of headaches during "tile counting" that is now necessary to get beginning of the level when you have multiple of them.

+1.
In fact, if I remember correctly, this feature was present in Pico v0.1.0, but has been (involuntarily?) removed in v0.1.1.

Holding down space will give you a grid with the quadrant you're in.

Yeah, but showing on the exact x/y would be better. If only there would be external map editor...