Sorry Dylan but "Cascade addition" doesn't make sense which is why there is no such feature. How would Access or any other RDBMS khow what the child records should contain or how many records it should create.
In 1-1 relationships, only ONE table has an autonumber as its primary key. That table should be the "parent" in the relationship. The related "child" tables MUST have primary keys that are long integers.
When working with 1-1 relationships, there is no need to use subforms. In fact, using subforms causes more work.
With a form/subform, the "parent" is added first using the main for. The "child" is not added until at least one field of the subform is populated.
With a single form based on a query that joins the parent and child tables, you still need to populate at least one field of the child record in order for it to be added.
Relational databases allow 1-1 and 1-many relationships to be sparse. That means that just as in real life, the 1-side may exist without a child-side. If your business rule is that the "child" is required, it is up to you to ensure that the child record gets added, even if you have to do it behind the scenes.
Referential integrity is intended to prevent orphans, not to create children.