I'm using Linux Mint 18.3 (Xfce 4.12) and have a launcher that seemingly can't be removed (any way I can think of; highlighted in the image below):
After updating a VPN client, there are two entries. One is correct and working (with proper icon, working directory and command) while the other points to a non-existent directory (and so fails to launch). MenuLibre editor shows only one launcher entry (the working one), as do
/usr/share/applications (per this question).
Editing either launcher icon via context-menu (right-click) doesn't give the option to hide it, either. Are there other ways to get rid of this launcher entry?