Many thanks for your replies. I like level editing, in fact, usually first thing I'm looking for in a game is a method to create (and maybe share) own levels, and this game has it while being fun at the same time - a rare combination.
I used to be experimenting around with modeling but I found it difficult and time consuming. I might give it a go again later but not this time. Nice that you offer your own models for editing though. Blocking off a line of the 3x4 seems the best solution so far.
I think the documentation is fairly clear, however I didn't work out at first that the layouts are somewhat fixed - as I see now. I could make layouts but the borders seem fixed - specific models; first I thought they're generated somehow. For example, I don't think I could make a 7x7 puzzle now (not that I want to, but as an example). Judging by your replies you seem to be the game developer(s) or close to them, and I heared you're planning expansion packs. I know this is no request feature forum, but I'd love a way to be able to contsruct my own border using tile-sized pieces that fit together. I know I could model these myself - maybe I will one day - but it's easier to ask here.
Also, thanks for your support and with ongoing support I can guarantee at least a few puzzles in a couple of weeks/months or so. My ultimate plan is to make a cube level where the camera is in it and you have to work on the inside of the cube... but that's just a long-term plan so far.
edit: also, just for the lol
managed to rotate it, but seems a bit shifted away
I know I could just copypaste from a default level, but I'm trying to learn here.
Now that I think of it, some reference on sizes would be nice (how big is a tile, the boarders etc.)