Given that add-ins for Visual Studio can use COM-based registration or XML-based registration and that the first one uses two locations (HKEY_LOCAL_MACHINE / HKEY_CURRENT_USER) and the second one uses up to six folders by default (Tools, Options window, Environment, AddIn/Macros Security section), when developing and troubleshooting add-ins I often wonder where an add-in is registered from.

I have filed a suggestion report to get this info in the Add-In Manager of Visual Studio 2010:

Add information of add-in registration in Add-In Manager
https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=466762

You can vote for it if you would like to have that info too.