Can't add user installed program to the "Open With" menu

[det4100]

Running LMDE UDP 5, cinnamon DE. I installed the program maxview from a .deb package as it is not in the repositories. I created a launch item in the Menu. I am now trying to associate the program with .max files. (paperport files). The program does not show up as an option in the "Open With" menu. I didn't expect it to. However, the add button is grayed out. I tried going through "properties" of a .max file. but the add button only adds the highlighted program (programs already listed) to the default open with list. I've tried this as both user and with root privileges. How do I get the "Open With" menu to add this program to the list. I'm sure I just overlooked something simple.

Thanks.

[Flemur]

Q: Can you modify the "open with" programs on more common files, like .txt?
-- If so, the .max file may have to be defined somewhere - glocal MIME definitions ...?
Edit: I don't think so; I created "a.max" of random numbers, "unknown type", and could set default via pcmanfm)

Anyway -

Check in ~/.local/share/applications (~/.local/share/mime didn't have anything useful on my setup)

I added the wine app "iview" - a stand-alone program that wasn't "installed" in any way - as a default for jpg files, and "Open with" via pcmanfm created the file: "userapp-iview-LU7WLW.desktop", and stuck more info in the file "mimeapps.list" (it also makes redundant .desktop files)

If all else fails you can probably add your own .desktop file and modify the mimeapps.list by analogy to existing files.
(My file locations are for mint/xfce).

FWIW, the linux implementation of MIME and associating defaul programs to file types out-windows windows; it's bad. IMHO, of course.

[det4100]

Thank you Flemur,

I'm poking around .local/share/applications and see that the Maxview desktop configuration file is there. It does not have the .desktop extension. I will look further into this and try to figure out the syntax to add it to mimeapps.list and have it associated with .max files.