I like this but can't think of a way they can implement it

is a certain hotbar slot a possability? or shift+ hotbar slot

Direct Control was meant for easier navigation/cruising when specifically controlling naval ships. To note, the feature is a relic of the past, for an old Movecraft that mainly focused on naval ships. As a personal comment I also can't see how this kind of Direct Control functionality (cruising vertically) could be incorporated smoothly into just the hotbar.

I mean Taakot if you sneak you can go downwards while cruising forwards but I dont know what would fit for the same but upwards,maybe sprinting? Idk?

is having such feature even possible at first place? if it is a matter of making it easy to use without it being annoying, perhaps i could volunteer to find a way to implement it smoothly ?