How can we add an assignee at various approval stages in RSSP?

Our organization is live with Redwood Self Service Procurement (RSSP) and we are currently facing an issue with not being able to add assignees to the approval workflow in the exact way that was available in the classic user interface. For instance, in the classic UI, users could click "Manage Approvers" then Add Assignee, and they had the option to add an ad hoc approver at a Parallel State, Start of Stage, End of Stage, or Start of Entire Task. In RSSP, it seems we currently only have the ability to add a parallel participant and we do not have the ability to add a participant at the Start of Stage, End of Stage, or Start of Task.