Apparently tilesets are not exported if they are unused. How do I force to export them? For example, one tileset represent the player, and there player do not exists on the map (just an object “PlayerStart”).
I have to add a tile somewhere hidden to add it to export.
Tiled does not currently filter out unused tilesets on save or export (though it could be a nice export option). So if you need this tileset to be referenced by your map even if you’re not using any tiles from it, you should be able to simply add the tileset to the map using the Map > Add External Tileset… menu action.