I'm creating a composite entity containing these two entites: SalesInvoiceHeaderV2Entity and SalesInvoiceLineV2Entity
Here is what i amended


The standard line entity already has a relation with the header, so i left as is

then i created the composite entity with header and lines and i put the standard relation on the line entity in the relation property of the composite entity.
but when i export the project, i get this error: Invalid relations between Entities