Hi Noel,
Yes, if you want to associate users with an action you would create at a minimum a content module and create user activity events for users and that content module. If you want to be able to cut lists based on what action a user took, you would create a campaign -> action_sequence -> page -> content_module. Creating this chain eases the migration towards using the Platform to serve your movement site's content.
If you need a very basic way of 'tagging' users with an action, you can use the 'source' field on the users table. There is a list cutter filter for 'source', so you can target everyone that is 'tagged' with an action.
Thanks,
John