Thanks, I guess that I'll have to learn JSON then...
I know a little bit of YAML, so I guess it shouldn't be too hard.
I wasn't aware of TileMaps and TileSets, thanks for the tip.
Though, reading your link (I didn't test it as a godot project yet) I wonder if it's not overkill for what I want : basically, my game will be a checkerboard with ships on it, and cards to be placed on columns, rows, or tiles to give these ships orders.
The logical grouping of tiles will be into rows, columns, ... so that when an order is given on a column (for example) all the ships placed on the column should apply it. Some effects will also target a whole set of tiles.
I want also to have "parent tiles" i.e my 99 checkerboard is also a 33 checheboard (i.e it's possible to give an order to the "left front parent tiles" that will apply to the 9 tiles that are in the 3 front rows and the 3 left columns), that would be another set of tiles.
Do I need a TileMap for that ?
Since in the definitive version I want to have a (2n+1) checkerboard rather than a 9*9 (n being the number of combat rounds as defined in the game settings, something that will be given to the combat system by FreeOrion) I guess I do (in order to use "autotile") but for the mockup is it useful ?
Writing this, I realize that the tiles would need to be in different sets (a single tile is both member or a row, a column, and a "parent tile"), so I'm not sure that TileMap is the right node to use...