Utilities

xdg-settings — get various settings from the desktop environment

xdg-settings get default-web-browser

https://portland.freedesktop.org/doc/xdg-settings.html

xdg-mime – command line tool for querying information about file type handling and adding descriptions for new file types

xdg-mime query default inode/directory

Unsorted

Desktop files

Directories

global	/usr/share/applications
user	$HOME/.local/share/applications

Run a .desktop file from terminal

gtk-launch <file>

Where <file> is the name of the .desktop file with or without the .desktop part. The name must not include the full path.

https://askubuntu.com/questions/5172/running-a-desktop-file-in-the-terminal

Set a variable in a desktop file

Exec=env GDK_SCALE=2 mediathekview

https://askubuntu.com/questions/144968/set-variable-in-desktop-file