This mod takes heavy inspiration from yyzsbackpacks but has been rewritten from the ground up to bring it to a more stable version, along with some changes to the way it works. 

Features:

You can shift click items from the backpack to your primary inventory

The Gold, Diamond, and Netherite Backpack includes designated bundle slots to hold smaller items and ensure that bundles are not entirely usurped.

Updated backpack design and crafting recipes.

Accessories support, so you can put your bundle into whatever you wish

  Credits:
yyz729 for the creation of the original mod, which is very good and I highly suggest checking out. Mod
SKO and SpencyRock for the excellent modelling and texture work