TBH, once the feature/task/project is done...you're working on something else and all those thoughts and TODOs quickly become stale.
CTRL-A + DEL is your friend, post-work.
The biggest value of keeping notes during a project is to prevent you from getting sidetracked by distractions. Write down the thought so it's out of your head, then get back to the task at hand.
DO NOT put them in your project backlog. That's how you get a 800+ list of items that get ignored and only add a huge mental weight to your backlog management. If you're going to ignore them for 3yrs and then finally delete them, why not start by deleting (not writing) them now?