Beginner asking for some help.

[daortir]

Hello !
Here I am, with a question about custom items. I'd like to know how make a custom item show up in my inventory, and becoming usable. I'm not talking about the ingame model. As an exemple I click on a mushroom which has the ingame model of a sewer fungi, and the player gets an item which would be a mushroom part in his inventory. My question is about the inventory item.