Dear Ann Landers,
I am using SQL Dev 18.3.0.277.
Going to Tools > Preferences > Database > Worksheet allows to set "default path to look for scripts".
When I save a worksheet, it defaults to this directory exactly as I would expect. But when I File>Open to pull in a previously saved file, it does not default to this location. Instead, it defaults to C:\Users\<myname>\AppData\Local\Temp.
Sign me - Puzzled