Yes, I have only reviewed ComBLAS's documentation, but would eventually like to dig into it deeper. A thought I had for distributed graphs would be something like support on top of a distributed store like citus, where shards hold subgraphs. This may be an interesting way to sidestep Postgres' 1GB limit on varlena objects as well.

Edit: I'd forgot to ask, do you have some ideas on the subject? I'm all ears.