Add an "Applications" guide, with links to net-default-browser, net-default-email, files-autorun, and files-open#default. Add pages for "Calendar", "Music", "Video", and "Photos". Explain how these are different than options in files-autorun. Link between pages. Add notes to files-open-#default about how you can use these options to quick set for a group of content types.

See also https://gitlab.gnome.org/GNOME/gnome-user-docs/-/issues/86 and https://gitlab.gnome.org/GNOME/gnome-user-docs/-/issues/8