Currently, you can sort for one workflow, and one assigned user. The list is automatically sorted by oldest-due (i think? it doesn't even say.), i don't think you can change this either.

I have multiple workflows filled with contacts, which each have different priorities of needing contacted. Additionally some of the contacts in each of these workflows are assigned to an agent.

Ideally, i'd like to have one master manual actions list, that every agent works off of. Where I could have it filtered by workflow priority, by assigned agent, and oldest due simultaneously.

So one agent would see on this list, the highest priority contacts which are assigned to them first. Then the unassigned contacts from that workflow. Then the lower priority contacts, assigned first, then unassigned. All sorted by oldest-due, but with that sort being lower ranking than the assignment and workflow priority sorts