I’ve been experimenting with Tiled as well, mainly to replace the barebones Paper2d tilemap editor in my pipeline.
Before you export your map, go to edit → preferences and check “embed tilesets”. With this option, Tiled will export the json containing a reference to the image file instead of the tsx, which Unreal cannot process.
I also suggest to export directly to your project folders, as paths are relative and won’t work if you move the json files around.
The only problem I’ve found so far is that you cannot re-import the map from that same json.
If anyone knows how to fix this it would be very helpful.