To outline in your head? I'm familiar with pantsing and outlining, but there was that one process I used to do in my younger writing years. Where you write down a premise sentence, and then give your mind time to expand on this core concept without writing it down. Then letting this idea have time to breath for about a day or so.
So of my early work got by fairly well on this method. Then jotting down rough notes (sort of like what one may refer to as way points), to help me remember where I left off. It wasn't until sometime later I needed a rough idea of an ending too. (It's was less important if I wasn't writing tragedy, where the hero presumbably lived on after the story.
Is this what is meant?
I found if I don't outline, that's when they start expanding to longer stories (for example 4,000 words). It's only when I use a seven point structure that I can keep a story well contained to keep it from bloating. But if i wanted to do a novella, then a looser outline would probably be needed.
The one that came to mind was Blood Of Katolinio, I think I may have focused to much on imagining to much, as one of my creatures was a demonic zombie with a shovel head. (Yea I was kind of random back then too.)
Oh and I'm so burnt out by science fiction. Yet my horror always becomes this.
To figure out all the scenes in your head and not write an outline down in advance.