for start,this is just a rushed not so detailed suggestion.
you know how the editor is so annoying when you decide to make highly detailed maps with a lot of tile differences,for that @ DC: could make a setting to where you could put 2 keybinds to swap between tilesets,or just press a and go left a tileset and d to go right a tileset.
This is in no way related to Steam functionality. So please stick to the thread that Yates suggested.
Moreover I'm not sure what you're talking about. Go left and right a tileset? There is only one single tileset per map. So tileset switching hotkeys do not make any sense in my opinion. You basically only selecet a tileset once and are done. Maybe you are talking about going one tile left/right IN the tileset (changing the selected tile)? That would make more sense to me.
Okay, then I understand. You are talking about changing the selected tile, not about changing the tileset. It would be easy to add hotkeys for this but I'm not sure if this would actually be very helpful as you normally want to select a special tile and not just the previous/next one and it's still easier to just click the right one instead of pressing a hotkey X times.
You can also right click tiles on the map to make them the selected tile. In case you didn't know.