Basically, what I am proposing is that you can create something like a shulker bag/backpack. This way, when you shift right click with it, it will not place it down, but will instead open it directly as a separate inventory.
would require a lot of coding and would be kind of pointless with the satchel thing being readded to 1.20
I don't think client side mods would be able to do that and it might be considered as a advantage compared over other players therefore breaking the rules. I might be wrong though.