Syncing users added to group in Central with users in host

We’re setting up our first Central Hub/Host service (so apologies if I’ve missed somthing obvious). I’ve followed the guidance in the (excellent) training " Working with the Citizen/Tenant Hub Framework".

As per the training, I’ve set-up the group in Central and added users to it.

When I submit a case, I can see it in the “Cases” tab in Central. I click on it, and it takes me trough to the Case details page in the host.

Step 1 of our process is for the case to be assigned to a user, so I’ve added a submission sub-page to the process diagram containing the following…

…when I view this page, clicking the drop-down only returns my own name, and not all the members of the group.

If another member of the group clicks on a case in Central to the host application, their name is then added to this drop down.

So - Is it possible to have this dropdown pre-populated with all the members of the group configured in Central? I suspect we’ll need to add some sort of ‘Active’ flag so that we can maintain the audit of users no longer in the group, but also not display them as assignable users?