You can save 1 "quick inventory" slot by putting the drax or any pickaxe in the the other slots of the inventory, and use the shift key to switch (not toggle, but holding it) between the drax and the block/whatever thing you're using. I know the video is old, judging by the version, but to this day there is still people who didn't know this so far, and still waste 1 slot there and has to use the numbers to switch between the tools. Even expert people and youtubers do that.. It's a so frustrating thing to see, for people like me who use the method I said.