Are you using dmenu or i3-dmenu-desktop? If you're using the latter, I'm pretty sure you can create .desktop files for AppImage apps so they're added to the list:
For myself, I've only needed to use AppImage once, and that's for a program that I only bother using from a terminal anyway; other than not showing up in dmenu out-of-the-box, I haven't had any other complaints.
https://build.i3wm.org/docs/i3-dmenu-desktop.html#DESCRIPTIO...
For myself, I've only needed to use AppImage once, and that's for a program that I only bother using from a terminal anyway; other than not showing up in dmenu out-of-the-box, I haven't had any other complaints.