In the description for the original organzier, JS500 said “it would be fairly easy to modify the card VP/theme card tray to accommodate the smaller theme cards”. I agreed, so I did.
The grid bottom was achieved using a height-range modifier in PrusaSlicer with 0 top and bottom solid layers. It's entirely optional.
The author remixed this model.
The remixed version comes in three parts: the tray itself (which holds the full-sized cards from Upstairs/Downstairs, same as the original), and two small insets that adapt the slots for the smaller cards.