Whenever I write new Flash Actionscript (that works) or find useful Actionscript, I make it a point to place it somewhere accessible where I can access it later. It may be years before I need that particular code again, but I want to access it quickly along with any associated notes I saved with it.
Here has been my solution for many years. I have added a personal wiki to my removable flash drive. As I write or find new code, I add a new post on the wiki, add appropriate tag, and paste the code along with any directions for the code. When I need the code again, I pop in the flash drive, copy the code and paste in right into Flash’s Actionscript pane. This has saved me many hours of hunting down code from prior Flash interactions that I have made or needing to write anything from scratch a second time.
If you need a personal wiki that can reside on your flash drive, TiddlyWiki provides one. There may be others out there, but this one works for me. Oh, get a nice lanyard to put your flash drive on too.