The SketchUcation toolset's Plugins Manager displays your Plugins' files by name order, and its Extensions Manager lists the Extensions' by name order too...
To order menus by the items' names is not practicable.
The files adding them load in alphabetical order, by loaded folder, but the menu item's name will never follow the file's name...
Back in SketchUp v5/6, when there were far fewer plugins, I set up a tool that did the restructuring of categorized plugins under plugins submenus, by renaming their files and editing their menu-loading code, but this is entirely unworkable given the explosion in the number of plugins available, and their complexity and the disproportionate efforts involved in updating any such setup, etc.