I sometimes create an "agenda" list for a project, where I can stash thoughts that aren't the next action, but that I don't want to lose. In my case, I tuck them inside an action in OmniFocus (almost the only use that I make of the multilevel hierarchies that OmniFocus supports) but I consider them, in GTD terms, to be project support material.

I'd consider this Organizing if I do it after saying, "Sheesh, this is a mess; let's clean it up." If I do it while working on actions and realizing, "Um...no, can't do that, but let's put it somewhere" then I consider it part of ...uh... what _is_ "working on actions" called?