You are overthinking it.

See my comment here - https://news.ycombinator.com/item?id=46986532

Also see a concrete example of an Engineering Notebook from a time when they were common, posted by user JetSetIlly here - https://news.ycombinator.com/item?id=46985832

On What and How to Write:

The book The Thinker's Toolkit: 14 Powerful Techniques for Problem Solving by Morgan Jones gives you a catalog of structured techniques for problem solving which you can use in your own writing.

Addendum to the above book's catalog would be "Decision Tables" (useful for all types of decision-making and not just software engineering); How to Use a Decision Table Methodology to Analyze Complex Conditional Actions Requirements in Software Development - https://www.methodsandtools.com/archive/archive.php?id=39