No, but you can set up something that looks like you have.
Remove the "allow creation..." option from the relationship. (This way you won't see the extra blank row in the portal.)
Define a global field to correspond with each field in the portal row.
Use this script to add the newly entered data into the portal:
Set variable [LayoutTableOccurrence::PrimaryKey ; value: $ID ]
Go to Layout [Portaltable]
Set Field [PortalTableOccurrence::Foreignkey ; $ID]
Set Field [PortalTableOccurrence::field1 ; YourTable::GlobalField1]
Set Field [POrtalTableOccurrence::field2 ; YourTable::Globalfield2]
and so forth for each portal row field...
Set Field [Yourtable::GlobalField1 ; "" ]
Set Field [Yourtable::GlobalField2 ; "" ]
and so forth for each global field
Go to Layout [original layout]
You can use an "add" button to perform this script or maybe a script trigger or two on the global fields could do the same.