A very useful Backpack Buttons mod by KhaineGB for 7 Days to Die.
Functionality has changed since TFP actually included the buttons already in the DLL, but they are disabled. So, you now have Stash All (does what it says), Stack All (only moves items to fill stacks) and Stash Smart (Moves items to a container if that container already has a stack or partial stack of that item. Will make new stacks). There is also a box with numbers in it. This box locks the amount of slots shown (default 0) so they are not affected when you click any of the buttons. It caps at 45, which is the entire, vanilla-sized backpack.
Since the code is already present in the DLL, this is just an XML mod + some new button icons so you can clearly see what they are. No SDX needed. KhaineGB has also tested it with his 60/96 slot bigger backpack mods and it’s working fine.
The forum topic of the mod is here.