Subitems: records inside records — Turn a table into subitems
Do it from the parent — the way you'd describe it out loud (“an order has line items”).
1. Open the parent table and choose Edit fields.
2. In the Subitems panel, pick the child table.
3. Press Make subitems of ….
RowFold adds the link on the child table pointing back at the parent (or reuses one that's already there). You never have to build the relation in reverse yourself.
Already have the relation on the child table? Open that table's field editor and press Make subitems on the relation row instead — nothing is recreated and no links are lost.