@Ihk You might want to try another workflow that does not break too many Access "good practices" and allows your users to feel comfortable with its autosave features. It's used a lot in the web forms, so people might feel familiar with it.
It basically involves creating the parent first, with as few required fields as possible. Upon creation, it will be added to a list of created items, all of them parent records. Each parent item will have an "actions" column to the far right with buttons like view, edit, delete, etc. If your users add a record and they don't like it anymore, they can just delete it before any children are added to it. If your users are fine with that new record or some other record, they can just click view, or edit and you see another form with extra info where you can add children and modify stuff. If the parent record is deleted, its children will be deleted too.
The advantage is that users will understand the relationship between the records by having the parents separated from the children and you as the developer don't have to deal with temporary tables or the like. Just one form is unbound, and that is the "add new" form, that's why it has to have very few fields, just enough for your user to identify it after creation.
Here's a demo.