Is there a way to merge two different graphs? Both are database-based.
I’m not at my computer this week but I know you can export DB graphs in various ways 
When you click the ‘Import’ button two of the options say “…into a new graph” but the one related to importing a SQL doesn’t.
Have you explored any of those?
Yes. But it does only allow for importing into a new graph. The option you are proposing asks for the name of the new graph right after selecting the compressed file. 
Blast ok. I hasn’t tested it. Have you tried asking over on the discord? The DB channel is very active.