part12studios Functions help to keep code organized and optimized. My function "StarageSave" in the example above can be called many times from different parts of the game. For example, when player finished a level, made some purchase etc.
You didn't notice "wait for previous action to complete" before, because it was only added in version r157 :) See that video link I posted.
Using "Wait 0.1" with asynchronous events is not a good idea, as sometimes the delay may be bigger than 0.1s
All actions inside one event are executed in sequential order. I'm not sure I understand what's your concern here.