I use subdecks to organize cards into different categories within a main deck. However, there are times when I’d like to review all the cards from the main deck, including those in the subdecks. Would it be possible to add an option to cram all cards across subdecks as well?
It is technically possible now. In the deck preferences for the main deck, there is an option to "Show cards from subdecks." When this is turned on the cram mode will include all cards from all subdecks as well.
The option is a little hard to find, and unfortunately it cannot be applied on a per-view basis, but I think it should work for you for now.