Well, even if you would plan on making more slots accessible over time you could just use a linked list (or ring buffer) and then shifting everything by one is actually quiet intuitive. But you would have to be a bit careful with the first and last element.
Cool interaction idea though. I was just playing the game on an chill/asmr level, so I did not really care about min maxing everything. But I could image that if the game gets trickier, that this is really a useful tool to have.