The system uses the recordid of the two tables (these are hidden by default but you can create these if you want to see them) (How to save a Record ID) to connect the records. It knows the user record and it just creates a new record in the Company / Home table that is connected to this.
You have to write at least one value to the newly connected record in order to get it to save. If you don’t need anything, consider adding a lastmodifiyuserid text field and place the logged-in-user name into it.
I simply created a decision checkbox field called Company Admin and set this to checked.
