MartinJ - some really good advice here, but this is my 2 cents. If some of the NAs triggered by the initial one are really short, then bearing in mind the "2 minute rule" just go ahead and do them, then you don't need to add them into your system. I can identify with how a next action can trigger lots more and sometimes its just better to follow those along and get them done, particularly if they can be done quickly and you have the materials to hand that you need. Once you hit a block, either in terms of time or materials you need, that may be the point to add things to your NA list. I found that sometimes I was adding things to the NA lists that literally took 2-5 mins and now I just do those as its not worth the effort (or overwhelm!) of adding them to your lists. It certainly made a difference to my flow and progress - and lists! In terms of tracking why you went with pipe A rather than pipe B, have you tried keeping some sort of daily work journal to record that? I come from a background of laboratory science and for years I kept a lab book that recorded what I did each day in the lab and the outcome of those actions. It also recorded information about materials I used, rationale and why I decided to take the next step in a process. The aim was to be able to go back and write up the work for publication, but if you need to record what you did and why, maybe something like that would work for you and remove it from your GTD system? That way only your NAs would be added to your GTD system and your other notes would stay in a dedicated book.