In a non-user-specific location in "application data":
C:\ProgramData\Autodesk\Revit\Addins\
In a user-specific location in "application data":
-
C:\Users\<user>\AppData\Roaming\Autodesk\Revit\Addins\ -
%appdata%\Autodesk\Revit\Addins\
In a non-user-specific location in "application data":
C:\ProgramData\Autodesk\Revit\Addins\In a user-specific location in "application data":
C:\Users\<user>\AppData\Roaming\Autodesk\Revit\Addins\
%appdata%\Autodesk\Revit\Addins\