Allows you to manipulate the available inventory, hotbar, armor and crafting slots on a per-player basis.
hotbar_slots = 18 in server config, max_slots_in_hotbar_row = 9 in client config
hotbar_slots = 3 in server config
That's the entire inventory
hotbar_slots = 18 in server config, max_slots_in_hotbar_row is either 0 or >= 18 in client config
hotbar_slots = 1 in server config
inventory_slots = 7, offhand_slot = false in server config