If I recall correctly, when I tried using DB Browser in Linux and tried to open my .sqlite file when connect with a read-only user I got that error.
I ended up copying the .sqlite file to a local writeable folder and opening the copy from three w/out issue.
Do you mean where in the UI do you point an existing job to a different database? If so, it is rather un-intuative as you need to use the job Data base menu then not just enter but actually CHANGE the existing database path which will then activate the buttons beneath the field.
