This is a concept I'm working around with Microdiagram (microdiagram.com) prototype.
i.e. having a general purpose diagram/graph layout is hellishly difficult, but most of the diagrams/charts follow much simpler rules, thus it's much easier to have N languages, each for 1 type of diagram, than 1 language for N types of diagrams.
While I fully support your efforts to make better tooling, UML is the poster child for this.
I highly encourage people working in this space to revisit those lessons.
Obviously if you find a new way to work around the limitations please run with it.
But limited scope, and targeted simplifications is the only way I have found, over application by trying to describe everything almost always ends up being more harmful in my experience.
Sounds intriguing. What is an example of a chart and its language that you have designed so far?
The Piano chart on prototype is an example, that's for discussing piano keys and chords on basic level.
I already implemented (in other prototype) diagram for event calculus (i.e. consideration of event stream through addition of new events like rollback, modify etc.)
On paper I have designs for point-in-time designs, scenario divergence and also some fun ones like a bingo card template. Diagrams are one thing, but there's also a design for collaboration and play-replay capabilities.
That being said, that's only a design right now with a simple prototype on the website :)