For me Action Support is the files and information I need for current active projects. My single folder holds labeled Action Support holds single papers I need that I do not expect that I will save once the action is done. If I think I will save it, even if it's a single paper, I make a file folder for it. That folder may be digital or paper but it's still a folder.
I actually have 3 "Action Support" places. One is paper, with a paper Action Support Folder and the files that are action support. The second is in DEVONThink and is both a folder for one off digital items and a series of folders for current active projects. The last one is on my main computer for longer files and info I do not need on my portable devices.