Yes, Quick Search will also list features in running add-ins/MapBasic applications.
The individual application don't need to do anything specific to get searched. The tool find the controls added to the Ribbon interface and list these amongst the build-in feature of MapInfo Pro.
Quick Search will also search the registered tools and search these using their name and description for the string entered in the Quick Search Field.
If it finds a registered application, the application will also be shown in the dropdown list.
If the application hasn't been loaded, the tool will be shown in grey as if it was disabled. If you click on the tool, MapInfo Pro will load the tool into the current session.