The gameconfig.json file contains some options that can be persisted between game runs.
This property adds extra search paths for tilesets. By default, the game looks in (folder containing the jar file)/tilesets, but if you have more tilesets installed somewhere else you can enter paths in this list to also search those paths.
{
...
"tileSetSearchPaths": [
"/home/user/shared/tilesets",
"/home/user/shared/downloaded/tilesets"
]
...
}