The way you wanna, no. It’s not supported.
(opinion below)
You can format a model in your application by pointing to each instance group (Dgraph set) individually.
It’s going to take more work (I believe). You need to configure unique PORTs and other configs for each instance group. But it is perfectly possible that way.
It is not encouraged, Cuz the characteristics of the Dgraph provide any need for that. Dgraph can split work between multiple instances. Create Shards and etc. There would be no need for RDBMS, technically speaking. But it is possible.
Also there is another way you can do by creating a gateway (application) in GraphQL pointing to those clients. It would be the same work of the previous, but it would be more organized and you would have the advantage of using GraphQL.