What is your software/approach to work with text?

This is an awesome idea, let me help you by trying to code this. I'll keep updating I'm this thread.

Maybe you'd like something like Scrivener.

For this kind of editing, I like to keep a scratch file (I use notational velocity, but any plain text file works) with sections denoted by Markdown pull-quotes `>` so I can track where I moved them from and what I'm thinking about them. I then use three octothorps `###` to denote breaks between "sections" which is especially helpful when I'm working across multiple documents.

I'll also use diff tools built into Vim/Neovim as well to show progress. I personally like the diffing feature and since I normally edit everything in a Vim-like editor it helps me stay focused with the tools I like.

tldr; I use Notational Velocity to capture ideas or copied text, then create an A and B document while I'm editing to determine progress. I repeat the process as needed. But not usually more than two or three times.

several folks I know use tools like Obsidian as a digital Zettelkasten for quick[ish] manuscript creation

I use it as a 'pure' note-taking tool

And I accomplish what you're describing ("eat a cookie ... have a cookie") straight in Word (or Pages)

I pretty much never 'delete' a paragraph/sentence/etc ... until I've figured out how I want to reword it - I just move it around and/or write around it until I have what I want

I put a big note in caps right above, or move it to the bottom of the file for later. Or just rewrite it immediately. Whatever it takes to stay in the same mental space

Some helpful advice for writing is to not be afraid to throw away what you wrote