Did You Know...
...that you can copy Access objects between .accdb/.mdb files by simply dragging and dropping them between their navigation panes?
This is much more convenient than performing a typical Access object import via the ribbon interface (External Data > New Data Source > From Database > Access...), especially if both Access applications are already open.
Items of Note
Be aware that you can only drop the object inside the target file's Navigation Pane (not the main Access canvas area).
You can copy multiple objects at a time from the source file. Perform a [Ctrl] click to add objects to your selection one at a time or a [Shift] click to select a consecutive group of objects.
If one (or more) of the objects you are copying has the same name as an object in the destination file, Access will give you a chance to rename the object. If you keep the original name, you will get one more chance to confirm that you really want to overwrite the object in the destination file.
Old Dogs Can Learn New Tricks
Maybe this isn't a hidden feature. Maybe I'm just late to the party.
Whatever the case may be, I think it's great that after nearly a decade and a half of developing applications in Access, I still have more to learn.
Shout-out to Colin Riddington of Mendip Data Systems for introducing me to this feature. Thanks, Colin!