Tilemaps: Non-contiguous Fill

I’d like to make a “dark world” element in my game and it would be very useful for me to be able to replace all tiles on a tilemap for a new tile. You could use the fill bucket for this or there could be an option to see the tile sets the tilemap is pulling from and change that source (this would be optimal).
This would also be useful for switching between two different looks to check them against each other and see which looks best.

I could do this in blueprint as well if there were a “get all tiles” function.