MichelDiz commented :
There are some issues that cover this in some ways
https://github.com/dgraph-io/dgraph/issues/1996
https://github.com/dgraph-io/dgraph/issues/4520
In the issue 1996 I shared some ideas about doing it with upsert block too. But the idea is a bit different from the issue itself. Cuz I promote it by doing Upsert Block instead of a new feature to the parser.
Supporting value variables in Facets with Upsert is a huge step to give support to this.