The Handcrafted Workshop is unlocked in the Prologues of both routes and functions as the game’s main shop. You are able to buy and sell weapons, armor, accessories, and items, but not everything is available from the beginning of the game. As you defeat the Shadows in the labyrinths, you will get item drops from them that can be sold to the shop that will unlock new items in the shop.
Some requirements to unlock items will overlap with each other, like if a weapon requires 3 of Material A and 3 of Material B, then an armor needs 3 of Material A and 1 of Material C, then you only need three of Material A and not six. The Workshop also functions as a storage for anything in your inventory, which only holds a total of 60 items. As with the inventory, items don’t stack and it only holds a total of 99 items.