I just figured out what you are all trying to do, and why it won't work.
You are all correct. You CAN'T select more than one old diagnosis from the drop-down list or from any list, using Dragon or any other means.
I was only trying to demonstrate to Chuck how I create problem-focused headings in my HPI section. I do this by selecting my diagnoses one at a time from the drop-down list in the Assessment section, just like you do, then selecting the whole list, copying and pasting it into the HPI. I then alter it as described above.
Of course, last month's problem list is still going to be in your new encounter when you open it, right? So what you are wanting to do is start a fresh one, using old diagnoses, and you are going to want them in a particular order. So, the best way would be to pick them out one at a time.
Once you have erased the diagnoses from the previous encounter, the quickest way to bring them back again is to go to the Previous Encounters tab, copy a previous Assessment section, and paste it in the Assessment portion of your current encounter.
If you want to clean up the clutter in the drop-down menu, you have to go to the Patient Summary, and mark all those one-shot diagnoses as "Inactive", or else delete them.