I tried adding esp32fs.jar to /home/myname/Arduino/tools/ESP32FS/tool (and a few other places as it looked likely that the jar file wasn't loading). I've definitely got the correct board selected, and can upload Sketches. I can also run the demo that writes to SPIFFS.
But the Tools menu doesn't have an option for ESP32 Sketch data upload.
Is SPIFFS data upload not available so far in V2?