These are the things I add in when adding in a new usecase to a codename:

- Expansion of the acceptance criteria into small steps.

- Any clarifications to what we are making

- Anything I don't understand yet so i can chase up someone about it later

- As I read through the code I write up possible refactoring opertunties. (I find this a lot better than adding todos as you can skim though the list closer to the end and address things that matter most first. Often the code that seems silly at first has a decent reason to be that way with the full context knowen)

All of this helps me pull the right threads without having to switch context throughout the day