Can't reassign the Presiding Officer

I can't figure out how our Presiding Officer, VPE, and VPM roles on our agendas (which were migrated from V3) are assigned, or how to reassign them. For example, our President is assigned to the Presiding Officer role, but she won't be at our next meeting, and I can't find a way to assign the VPE to that role for the next meeting. Help?

Please note: I read the "Assigning Speaker Role" topic and it seems to describe a similar (if not the same) issue. Also, I read the info on the Agenda Roles documentation page (https://support.toastmastersclubs.org/doc/fth4/agenda-roles).  

Per the Agenda Roles documentation page, I changed the Presiding Officer, VPE, and VPM roles so that the box is NOT ticked for "Members may sign themselves up for this role" (it was ticked by default). The migrated agendas already show these roles as roles that cannot be signed up for).

Thank you,
Beth May
Frederick Toastmasters, Club 1082
Website Admin