Another Windows work around is to create a batch file, say “RT.bat” containing the following
if not %1=="" “C:\Program Files\RawTherapee\5.3\rawtherapee.exe” -R “%~1”
and setting this to be your default program for whatever type of files you choose.
Works well for me with FastStone and Photo Mechanic
If used a few times in W10 File Explorer with “Open with” > “Choose another app” it will stay in the list so quite easy to invoke on an ad hoc basis
Need “” around %~1 to open files with spaces in name