I found many unity applets from another question Is there any tool to manage them as in the case of gnome2 ? ie, moving applets ,enabaling and disabling applets from a list etc
Unity does not have applets, as you suppose. They are separate applications which show indicators, and there is no central place to manage them, reason being that they are meant to manage themselves.
If you want to add or remove indicators, you either run or quit the application(s) as needed. Some applications also provide the option to disable the application indicator.