Thanks for the demo link that was helpful. I solved my problem experimenting on that.
I created a one to many using notes module as the primary and contracts as the related module but the subpanel didn’t get created, so I did a bit more digging.
On this topic it said it had to be a many to many for the subpanel to be created. I created the same relationship but a many to many this time and then a new subpanel was automatically created but it was empty (no name and no create note button) I ran a quick repair and then it worked.
Edit: There is still one problem. When I go to notes there is now two subpanels for contracts.