On Tue, 12 Nov 2019 17:56:26 +0100, "R.Wieser" declaimed the following:
To be fair, Applications/Preferences Main Menu Editor gives a graphical way to edit the main menu, including reordering entries (just spotted it while looking for something else: Debian xfce has a "Mime Types Editor", but does not have a Menu Editor)
Suspect you could specify it on the .config/mimeapps.list (I think the common "Text Editor" is mousepad.desktop). Commenting out the text/plain subclass for text/x-python meant LibreOffice doesn't come near it
{I also discovered that GNAT Programming Studio sticks its icon file in a non-standard location, so I had to put in the full path for the icon on its .desktop file. Now the menu shows the GNAT "G"}
Still a touch faster (especially if you have multiple types to work with) to hand edit the .config/mimeapps.list file...
Okay -- too many OSs here (and I haven't even attempted to use the graphical environment on the BeagleBone Black, which is LXQT). xfce uses Thunar.
Open With... seems to add whatever one picks. Just that, unless [X] Set selected was picked, it does not become the default for double-clicking.