If you are looking for the location where the Revit Addins are stored you can locate them in the following location:
If you recently installed an addin and Revit is no longer behaving as it should you can test if the addin is the problem by removing it from the version folder.
Make sure that Revit is not open when you remove the addin from the folder. Launch Revit and see if it works properly.
To test without any addins you can move the entire folder to a different location, again while Revit is not running, launch Revit and test functionality.
We have seen instances where one Addin will interfere with another which causes issues in Revit so it may be necessary to add them back one at a time to see when the issues arise.