Seems to be largely missing...or am I overlooking it? (see attached for example)
See Opening Files in Other Applications (https://www.photools.com/help/imatch/#file_management.htm?dl=h-3) and Applications Favorites (https://www.photools.com/help/imatch/#fav_basics.htm?dl=h-12)
Tip: You can find this info in the IMatch Help System (https://www.photools.com/help/imatch/) by just typing in open into the search box at the top. The 3rd link opens the general File Management topic, which covers this and all related tasks. Expand the table of contents at the top to quickly navigate to the topics you are interested in, like opening Files in other applications.