Am I missing this, or is it not a thing?
Can you delete elements off of a mood that you’ve copied? What is the best way to create completely custom from scratch Moods? With NO extraneous elements?
I’ve watched the videos, but I haven’t seen this one yet, unless I missed a video in the series?
Yes just click on the element and then from the element properties tab click delete
You might find the tutorial videos that we put together helpful, here’s a link to the first one 
To create a new mood you just need to click the plus icon in the lefthand panel. that will create a brand new, unnamed mood, within the current soundset. You can then set this up how you want it and click “Save Current State” to save all currently playing elements as part of that mood
So just to confirm.
There is no way to start with a completely blank soundset?
There is no multi-select to delete out the 40 custom sounds that I do not want in a soundset?
To start a blank soundset click the plus icon on the left hand panel, where it shows the list of soundsets. Same with moods, click the plus icon on the left hand panel when you are in a soundset. Likewise to creat a new element click the plus symbol at the top of the screen in the centre panel.
Wherever you see a plus icon you can click that to create something new, be it a soundset, mood or element 
Ah. Ok, I see that. I never saw that in the videos so I was lost. I apologize for being obtuse.
Not a problem at all. The Creator is a powerful tool and does have a bit of a learning curve, but once you have a grasp of the basics it’s actually pretty easy to learn and create awesome sounding content