I have a really easy use case but looking for help I'm trapped by most of the docs referring to the old workflow UI.
JSM - Team Managed project.
WIP workflow:

On awaiting approvals I have:

If I click on "At least 1 approver..." I can set it up as per below with "Approvers" as the approver field. I believe this was the one built into JSM.

All that works...if you want to add individual users and have them all needing to approve to be able to move the issue onto "Done".
However - I want to use Groups. So I have set up three groups in the Jira Directory with two people in each group. I then found I had to add a group picker (multiple groups) field to the screen, which I did. Again, I picked a default JSM field called "Approver groups". However, when I go back to the image directly above and try to find that in the "Select or name the approver field", it isn't there and only lets me try to create it.
So in summary - how do I get the Groups that I set up in Jira Directory to be the groups used in the approval process? It's driving me to distraction!
It looks like the old workflows UI had some more options I'm just not seeing in the new one.
Thanks