I'm trying to load 2 records (1 child and 1 parent with a FK attribute in child to the parent) via REST

I had try to file the FDN_Parent field (in Child) with the Name of the Parent (the Name is used in DisplayCard of Parent) but it's doesn't work.

The only way I see is to used the FID_Parent but the Parent record havn't yet an ID)

Who can I do that?