I can relate at least to a degree. Thankfully there's nothing physically wrong with me, it's all mental. And it's not even like severe depression or anything like that. I just go around feeling disconnected from the world, even when I'm ostensibly out in it. At the least, social interaction just takes so much energy that it's not something I can do for extended periods, and ADHD means that I have a hard time putting the work in to maintaining relationships a lot of the time. Plus a lot of other people are boring. Plus we all have 8 million things vying for our attention and time.
This is still something I'm trying to figure out, so unfortunately can't go any further than this.
Regarding the twine-like thing, what is it exactly that you want to be able to do that a simple text editor can't?