XD
Well, the current implementation isn't bad, it's a new learning curve! The four buttons would be easier, yes, but this should stay too, kinda like the Minecraft/Stardew Valley hotbar! You know, press 1 goes to slot one, press 2 slot two, scroll to change fast and vice versa.
But hey, it was a game jam, the game is heck good, the best I played that's for sure! Congrats :D