Hello,
No, currently this can't be done because adding user to a group means modifying the group, not the user. Thus, adding a user to 12 groups means performing 12 operations on 12 different objects.
As an alternative, if the groups don't change depending on a user or if the groups can be derived for each user based on certain properties, for example, based on the user's department, you can use a script to add users to the groups. In this case, you can have only 1 Approval Request that will be generated before running the script.
For information on how to use scripts for group membership management, see the following tutorial: http://www.adaxes.com/tutorials_Automat ... cripts.htm.
To request approval for running the script, enable the Get approval for this action option when defining an action that runs the script.