is there some kind of folder like structure for displaying / undisplaying sections of code?
Yeah, basically. Any events you put into a group can be collapsed down to just one line in your event sheet.
Another benefit of groups is that you can activate/deactivate them at runtime. Say you have a bunch of events that you only want to run at a certain time, like inventory menu controls or something. You can have them deactivated most of the time, but when you open your inventory menu you disable your play control group and enable your menu control group.
Another good way of sorting your code is by including separate event sheets. This is what my main event sheet looks like:
There are no events... just includes to other event sheets. Each sheet has a specific purpose. This keeps things tidy and modular... for instance, if a level doesn't have the shotgun enemy in it, you can just leave the "Enemy - Shotgun" event sheet out. If a level has moving platforms in it, just include the sheet that runs your platforms, etc.