Great question from @John Whidden yesterday on the Drafting Class - so I thought I would capture the answer here.
If you create a Dynaview Collection of 1 or more sheets, you can create additional sheets by copying one of the dynaview frames that was created for the Dynaview Collection, because it is a copy it carries the properties of the original frame and adds it to the Dynaview collection. You can then run the build Sheets command to build the sheets for the sheet set.
Remember when you Build Sheets, that any work that you have created already will be deleted and then the sheets rebuilt so be aware before doing that.
If you want to “Insert” a Sheet into a set of Sheets that have already been created so that you do not have to rebuild the sheets to add the extra dynaview of the collection to an extra sheet in the sheet set, then you can create a custom sheet in a custom sheet set and then you can move it into a Plan Grid based Sheet Set by changing its Sheet Set property in the properties pane. You will have to add the dynaview manually in this situation, however it is still better and quicker than having to blow up an existing Sheet Set to achieve the same objective.