I have a use case where I am integrating an application that has been used by the org since the start. There have been a few different username conventions over the years. We are locking this down moving forward.

When we add users to the application we will be in the position of having to update the user names for those who don't conform to the current structure. Just wondering if there is a method to do this in bulk? I would imagine one could create a custom attribute such as xyz_app_username and then use that for the application username.. That would allow us to import a user csv with the custom attribute xyz_app_username update which would overwrite the current value. ( found I could use the chorme extension rockstar to basically get a user csv that I can use to recreate the import users csv ).