NotifyVisitor's javascript tagging API allows you to send in any metadata you need to associate with a user or a session so that you can filter against it.

Recognize individual users. With one line of code, you can brief NotifyVisitors which user is being recorded so that later you can see users with a particular email address or ID.

Capture interesting events. If you're curious about watching all session recordings where a visitor pressed the play button, you can tag those session recordings with a tag like "pressed-play".