My full time job is as a User Experience designer. I study users to understand their needs, mental models, and design software that "fits" their brains. One of the key measurements I utilize to evaluate a design is cognitive load. Put simply, cognitive load is how much "brain effort" it takes to learn and understand something.
Trading is a very high cognitive load activity. Learning to trade even more so. When I set out to learn trading I immediately looked for ways to eliminate as much "extra" thinking as possible. Hence the streamdeck. Memorizing hot-keys takes effort, and while I'm trying to juggle chart signals, make planning and position-size decisions, and execute good risk management I don't also want to be trying to remember which hot key I set to buy 500 shares. By using the stream deck I don't have to remember, because my hot keys are visual, right in front of my face.
Next to my membership here, I'd say the Stream Deck is the best investment I've made in my trading.