Studio sessions are great for quality control and reviewing plans. It would be great to have a plan development workspace with the collaboration of a Session but the ability to add / delete sheets within a set.
Not sure if I've ever seen an explanation for why a Session doesn't allow adding/replacing files and/or pages of a PDF — is it a programmatic difficulty or a decision about how 'control' should work in a Session? If it's the latter, then a third type of Studio (Project, Session, ______) or simply an administrative option to create a Session to allow or dis-allow this new flexibility would be very helpful. There are many workflows where the ability to flexibly update PDFs in a Session would be a great improvement.
(If this is indeed simply a decision on Bluebeam's part of how a Session should work, then it's yet another example of the program's development being driven by one (or a very few) specific workflow(s), with apparent blinders — and sometimes active resistance — to the existence of other workflows with different rationales or needs.)