Yah I just watched a video highlighting modded version of the game. I already thought valheim was pretty empty and kinda blah but after watching that video with all the mods it stunned me just how BLAH this game really is after all. O well time to mod it up for some real fun I guess.

A quick Googling (query=valheim+mod+armor+slots) gave me this as the first response: https://www.nexusmods.com/valheim/mods/92

I don't use mods, but it seems to do exactly what you want.

https://steamcommunity.com/app/892970/discussions/0/6620894968760113655/#c6620894968760417144
I recommend all of them but BetterArchery & EquipmentAndQuickSlots are the ones you probably want.

I use AzuExtendedInventory for Armor and Quickslots. Works great.
(Also recommend Thunderstore over Nexus for modding.)