Run as a specific user/group ?

[timespaced]

Got the app up and running, works great (THANK YOU!)

However, it runs as administrator (I'm on QNAP for reference).

I tried adding UID and GID environment variables to assign IDs, but it doesn't work.
Is there anyway to have files saved as a specific user? That way Plex (hosted on another system) can delete files when I'm done watching them.