I have many plugins from several companies. Some companies plugins just go the main menu and create a mess, some companies plugins go into nice sub menus. It´s sometimes hard to browse through many pages of menus and fing the right plugins.
So how can I customize the plugin menu?
If they’re VST2, you can go to your cubase install directory, open de VST plugins folder and the filetree there is the same as how they appear in Cubase. You can move .dlls around to put them in the location you want them to appear. If they’re VST3 you are out of luck, the manufacturer of the plugin determines where it shows up 