I know that Photo Mechanic Plus does not support ON1 Photo RAW nor Affinity Photo. However, for those of us who use ON1 and Affinity instead of Lightroom and Photoshop, PM+ does give us a generic icon for the native files from these apps. These images can be launched from PM+, too. Thank you for that ability.
One has to be careful, however, if thumbnails for these two formats — ONPHOTO and AFPHOTO — are side-by-side in PM+. It can be confusing because of the identical generic icon with almost identical extension names superimposed.
The Finder renders thumbnails for these two files by picking up the embedded JPG in the AFPHOTO file and using the generic ON1 thumbnail for the ONPHOTO file.
The same rendering strategy is used by ACDSee Photo Studio 8:
Is there a PM+ setting that would better distinguish between files to the two formats without cluttering the contact sheet with .xmp, .on1, .dop, etc. files?
Maybe render the thumbnail in the AFPHOTO file?