Vercte's Satchels adds one item: the Satchel.
The Satchel is an item that unlocks six extra slots in your inventory, located below the hotbar.
Once equipped, its contents can be swapped with the first six slots of your hotbar using a keybind (default V).
This can be very useful! Use it to store extra building blocks, tools, clean up your main hotbar, or just use it as an inventory extension—because it is one. The Satchel also integrates itself seamlessly into vanilla container UIs, as well as working with Modded UIs.
Satchels is intended to be configurable in behavior by the client (changing the position of the satchel) and in common (changing which UIs the satchel appears on).