Not sure what you are asking. You can add functionality to the back end by using the utilities style 'plugin' but this is a new feature in the development stream (nightly builds.) There are a couple of examples--backup_restore and schedule_content.
This mechanism places a button on the overview page of admin.
To modify other admin menus takes making changes to the admin scripts.
The admin toolbox is not an interface we built to be extended. It could be replaced with a plugin. Then you could just create a different version of that plugin with the interface extensions you want.
This seems to be a good idea, so you will likely find it implemented in a nightly build soon.
Digging this thread to know if it's possible to add tabs in the admin section?
I want to add a feature to upload pictures in my gallery. And I want to add it as a plugin (maybe others will be interested)
So I'd like to know if from a plugin, can I add tabs in the admin?
If no, can I add feature in a existing tab from a plugin?
Thanks