Right click mouse menu

Is it possible to add commands to the right click mouse menu in dopus?

Yes, have a look in -> settings -> customize -> context menu -> lister context.
When you click on the "view" button at the right, you can not only see the current menu, but also can right click
in those menues, to make new menues or buttons.

What you need to do depends in which menu you want to edit.

Oh, off course there are the context menu settings for "files and folders" etc. in the file types submenu.