What's the best practice for working on a Mail Merge based document, not completeing edits in one go round, and then continuing edits later?

As an example, we have a writer merge template that pulls CRM data and will ultimately end up in Sign to be sent to clients for signature. From CRM we initaite the merge which of course opens the template in Writer ready to merge. We then make changes to the pre-merged document (not the template). There are instances when all the edits won't be done in a single sitting, so what's the best approach to in effect save that version of the not yet merged document so we can come back to it later to continue editing before finally running the merge for the given CRM client?