There's no such thing as a 'session'.  We do store "work in progress".  It's tied to a user at an organization - whether stored as a DocumentReference or as a QuestionnaireResponse.  The only thing we need to say is that in order to continue work on a work in progress:

• user must be from the same organization
• user must have authority to access the patient (i.e. launch from patient context)
• user must have authority to use DTR

Beyond that, DTR imposes no constraints.  If EHRs want to impose additional constraints or negotiate with SMART app vendors to introduce additional business rules, they can.

In terms of lists to work on, we shouldn't be talking about Task at all.  The EHRs have expressed no interest in Task.  What matters is that there's an order that either has a flag on it that says it's DTR relevant (from CRD or local processing) or someone just selects an order and says "do DTR on this".  Any section that's talking about "how do I figure out which QRs or orders still need to be worked on" needs to be in the section on launch and needs to focus on what the SMART app will do in terms of query.  How 'full' EHRs manage it is outside our scope.