I don't use terminal to do that, what I do is a search in the menu search (or Synapse), I type "mozo" or "menu", open it, and this window opens
I select "Graphic" and add a new item, a window dialog will open again, I at "command", I browse and link directly the appimage, and for the icon I download one from the internet and same as "command" I browse my directories up to the icon, input a name I want and a comment for when hover in the menu a little explanation appear after a second or 2
I do this both in Ubuntu-MATE 20.04 and MX Linux 21 (Xfce DE)
I select "Graphic" and add a new item, a window dialog will open again, I at "command", I browse and link directly the appimage, and for the icon I download one from the internet and same as "command" I browse my directories up to the icon, input a name I want and a comment for when hover in the menu a little explanation appear after a second or 2
I do this both in Ubuntu-MATE 20.04 and MX Linux 21 (Xfce DE)