The gods as my witnesses, I will force it into existence

"In a hole in the ground there lived a hobbit" - J. R. R. Tolkien
That is just how all good things start; with a small idea that grows. Same with anything creative.
- He referred to the whole legundarium as growing from a single small idea. I don't know if we know what it was, but it started that way.
  https://wikipedia.org/wiki/Leaf_by_Niggle
- Same for Game of Thrones by G.R.R. Martin... He's stated that the whole story started from a vision of the "king's party comes across a dead direwolf surrounded by her whimpering pups and the stag that pierced her chest" scene.

Guilty. Though it usually stays in my head so I can go back and re”wtite” it over and over until I accidentally make huge plotholes but I like the scenes that cause plotholes so time to redo THOSE while trying to not make the scene suck. Rinse and repeat.

Isn't this kinda what you want?
I am an uncontrollable perfectionist in this scenario. I have yet to start to write down any of the narratives that have lived in my head for years because i feel the tiniest detail or Nuance needs a research paper of its own for it to make sense.
I am more likely to die of old age then write a single chapter but someone is going to inherit a huge collection of neo-science articles.

Absolutely called out. So many stories either on random document/text files or on Wattpad that are so incomplete it's not even funny.

Short stories and flash fiction avoid this problem by having genre conventions that allow for focusing only on a specific scene. Ploughshares in its recent Winter edition has a fiction piece that's three paragraphs long, which I thought was an appropriate length for the content.
I think it's somewhat common for writers to start with writing shorter pieces. GRRM comes to mind.