I’m getting this problem too. Nothing stacks anymore.
Hopefully this isn’t by design – it’s a huge pain to scroll something from the bottom of your inventory, to midway up your inventory, to close to the top of your inventory, just so you can equip it.
There is no item stacking anymore as each item is unique with their own durability (and in the future, properties). I do have plans for “smart grouping” of items; however, in the meantime, simply use the inventory filter. Equipping something was still a pain before with stacking, the filter will allow you to equip faster than before.