How appropriate, I often have many GitHub issues and corresponding PRs which chip away at problems that are not yet solved. They usually start with some naive approach that doesn't scale. The reasons for its unsuitability to ship are listed then iterated upon. Sometimes work done elsewhere by someone else or myself will find relevance and move the ball closer to the goal. I've always thought of this process as "gardening PRs".

My other process is Emoji-Driven-Development where a whole lot of these PRs can be listed (with high density) and only a single emoji indicating each development status. It's good for refreshing the mental list of unsolved things and where/why they're stuck.