There is no capability within FHIR to execute a sequence of queries with dependencies between them unless we get into something like CQL - which is outside the scope of what we're trying to do with CDex.  The objective isn't to fully replicate the query mechanism complete with continuation pointers and wrap that inside of a CommunicationRequest.  Instead, the intention when using CommunicationRequest is to use FHIR's query mechanism to define the sort of data desired, but allow humans within the provider environment to gather/review/filter the relevant data and return all of it.  Query continuation/paging mechanisms aren't appropriate for that human-involved use-case. When it is possible to query directly and page through the data without human intervention, then standard FHIR RESTful search should be used and CommunicationRequest would not be involved.