Feels like it was started before LLMs, and now this pitch is just trying to incorporate them after the fact, as opposed to rethinking your thing from a deeper level, now that the world has changed.
Seems like you have a unique skillset in having some mental machinery to view the world in your 2D grid/node based paradigm. If text brainstorming was your use case, I think ChatGPT has killed that. If I'm gonna visually brainstorm I'm gonna use pen and paper, and if I'm going to be on my computer doing text brainstorming I'm gonna use ChatGPT. I don't think the lines provide enough value (chat GPT does bullet points well and can also generate graph viz)
Is there some end-product your tool could produce that users want, and LLMs can be used to help make those? Or can you take more advantage of your 2D + grid/node based tool to provide something more than an obscure text editing experience? For example, perhaps using mathematical distance as a first class citizen, adding physics, et cetera (I have no idea what would be useful, just that perhaps there are some "magical" things that a node tool could do that a text/chat interface will never come close to)