Multiple records in embedded form

On our customer record, we are wanting a couple of embedded forms, 1 showing their PCs, one showing their mobiles. Both are configured as a 1-Many relationship.

How can we step through the multiple records in the embedded form when a customer has multiple devices?

We've tried "step through children", but cannot figure it out. Tried adding a button to use "next record" action but even though it's in the embedded form, it moved the parent record (customer) to the next record

Any help or advice appreciated.