Is there any way to create foldable regions of code in ActionScript 3 (read this as Adobe Flash CS3 built-in editor). I'm looking for something like in MS Visual studio so that I can do:
#region "Event handlers"
... big list with methods here
#end region
Any ideas?
I don't know if it's supported. Seriously consider a 3rd party ActionScript development environment, such as FlashDevelop, a very well thought out alternative. It's a massive pain developing in the Flash IDE.
No there is not really anything like that in Adobe Flash CS3. CS4 introduces conditional compiling, not really what you are looking for; but it does not get any closer.
Like already suggested, I would suggest using FlashDevelop. It has some folding options, but event more importently it has intellisense and automatic code generations. And it is free.
Flash CS4 has a code folding feature. Just select/highlight a few lines of code and click the - icon on the left.