> What was the name of the one that allowed you to specify the diagrams using some custom DSL which in turn would generate the diagrams themselves?

I think the recent one on HN that meets that description was D2 (https://d2lang.com/), though that description fits a lot of tools.

Yes, it was D2! Thank you a lot!

Note to self: IIRC author said I can do it locally from browser now, should work without connectivity.