Whenever you get a page or portlet corrupted restoring it to the default or similar to another user's configuration looses all user's configuration.
One precaution against that is the user personally documenting the changes.
Another is the admin keeping a list of the URL's of the configuration pages so that the user can access the configuration.
That a list of the bookmarks referred in the TEC DOC.
However, if the configuration is a pop window like in the currently supported versions, the bookmark URL needs to be manually edited and cannot be used as it is
(javascript:navigateToURLTarget('modalrefresh','app?action........)
While on the configuration page the user can document the content, filters and layout. On the content tab of the configuration the Overview page General tab you can see the portlets, but you cannot access their configuration pages. The admin would have to get their URL's from another user.
Without going to the database for the latest user modification the user might recall that by looking at the content. If the user does removing that and replacing it with the default could solve the problem while keeping all the other customizations..