I use to edit a .desktop file to remove some categories so that a program appears in only one menu item. But if I reinstall the package (apt install --reinstall ...) the editing ("Categories=" field) is lost. Is there a better way? Thanks.
Okay found another way; this is for all users.
sudo mkdir /usr/local/share/applications/
and move your desktop file there. I made an own starter for mpv (with some options for playing DVD's).
mpv-dvd is my own starter. I remembered one's uppon a time it was the way to make starter on your own. It seems it is still respected. It is also in my application start menu. (tested in lxqt ubuntu jammy)