TillaGoto is a tool that allows you to quickly list all functions, labels and hotkeys (FLHs) in a script and go to their definitions. In order to bring up the FLH list, press F12:
You can also go to a FLH by middle-clicking on an instance of its name in the script. If you want to go back to where you left off, press Alt-Left. In a similar way, Alt-Right takes you back to the FLH definition.