The current Solus MATE 3.9999 ISO has menulibre installed by default. Menulibre is non-functional out of the box in Solus MATE (https://dev.getsol.us/T5807)
Now that the official MATE menu editor (Mozo) is in the Solus Repos, IMO it should replace menulibre in the Solus MATE ISO so that the right click brisk menu | edit menus function is working 'out of the box'