This app looks absolutely phenomenal, gzip!
Great work on this app, will give it a look for sure.

I wanted to ask, does this allow us to create new column entries for Zelda 1?
Or we can only see them?
I ask because I want to be able to edit certain places for Zelda 1 so they don't look as blocky.
For example, the two islands in the middle of Hyrule, where both the 1st and 4th Dungeon are located, look extremely blocky for my taste, and I'd like to add some custom columns to add some of the diagonal rock tiles, kinda like how the screens are in the Fairy ponds, but I know those don't have any water tiles in their outer sides.
Something like this:
Original / Mockup

I want to do the same for other screens that look too blocky, and spice them up a bit so the look a little bit more "ragged". I want to do the same for the following screens based on this map for the locations:
https://www.supersoluce.com/sites/default/files/node/53892/solution-zelda-1-nes-carte-du-monde-worldmap.jpgB-3, B-4, B-5 (make them like the graveyard A-3, A-4, A-5 parts), C-3, D-4, and finally islands F-5, H-4, P-1, P-2 and P-3.
That's why I'm asking, I wanted to improve some of the screens in Zelda 1, and I believe I will need creating a handful of new columns for this.