I assume you are using the SketchUcation toolset ? In v2017 SketchUp introduced its own Extension Manager [Window menu v/ Preferences] The current SketchUcation toolset includes the ExtesionWarehouse³ AND Managers for Extensions and Plugins. In effect all RB [Ruby] files installed in your Plugins folder are 'plugin' files, and these are auto-loaded as SketchUp starts. Simple RB files load and offer some functionality. Other RB files have a supporting subfolder of scripts to add functionality. These 'Plugins' appear in the SCF 'Plugins Manager' and can be disabled/enabled. Other 'Extension' RB files also have a similar subfolder - they are defined by their authors to be a particular subset of Plugin - 'Extension' - that is mandatory in anything available from the EWH. These files load like other Plugins, but if the are disabled using the native 'Extension Manager' OR the SCF 'Extensions Manager' then they are not displayed in menus or toolbars etc. If you disable an RB file using the SCF Plugins Manager, which might have loaded an Extension, that possibility is sidestepped. So you can enable/disable both simple Plugins AND complex Extensions, if you disable the 'loader' RB that would have loaded an Extension it never gets listed... Note that NOT all scripts load main menu items - some are run from the context-menu, or are 'helpers' or run from Ruby Console - and then their menu items are not restricted to the Plugins [now renamed Extensions] menu