It looks like you're new here. If you want to get involved, click one of these buttons!
To prevent me from accidentally add stuff to the wrong layer a lock tool would be useful. It would be useful, especially without the abilities to select tiles and move them to another layer when you place them on the wrong one.
Even without a lock, I think 90% of my mistakes of this type could be avoided simply by not selecting a layer when its visibility is toggled. Almost every time that I draw on the wrong layer in HK, it's because I hid a layer, then forgot to re-select my previously-active layer before trying to draw on it. And then this is compounded when I start scribbling around, trying to figure out why it's not drawing (because, although it is drawing, it's drawing on a layer I can't see... so then I need to unhide the layer, fix what I accidentally drew on it, and rehide it before going back to what I was originally doing).
Done this a dozen or so times just in one map... and the converse, though that is more obvious and there is less searching.