I use RawTherapee (5.8) to edit my RAW files. I used the following address in RT's "preferences" to ID the location of my photo editing app, Affinity Photo 2, and successfully mapped the "send to photo editor" button in RT to Affinity Photo 2:
C:\Users\XXX\AppData\Local\Microsoft\WindowsApps\AffinityPhoto2.exe
(Where "XXX" is your personal user handle.)
You may have better luck with this (I did not try this, because the above address worked for me):
C:\Users\XXX\AppData\Local\Microsoft\WindowsApps\SerifEuropeLtd.AffinityPhoto2_3cqzy0nppv2rt\AffinityPhoto2.exe
A search of your own computer (for "AffinityPhoto2.exe" or "*photo*.exe") will locate the executable on your computer. In the search window, right click on the file and select "show in folder". Then copy and paste the folder's address into the preferences of whatever app you're setting up, and add "\AffinityPhoto2.exe" to the address. Save your preferences.
