No sub-tasks.
The Inventory GUI is a GUI you can open when on the HUD. You have the toolbar, but you can also have tools stored in your inventory. You can only have a maximum weight in the inventory.
The inventory system is also on vehicles. Vehicles have their own inventory that saves on them.
UI location: inventory SCREENGUI
[IMAGE: picture of inventory UI]

Title bar: "INVENTORY", with a weight counter top right showing current / max (e.g. 0/20kg). The X closes it.
Item grid (left): each item the player is carrying gets a frame, with a quantity (x1) and the item name. Tools stored here are separate from the toolbar.
Detail panel (right): when an item is clicked, shows the Item Name, a preview, the item's weight (e.g. 1 KG), and a Description. Two buttons: EQUIP (moves the item to the toolbar / equips it) and DROP (drops it on the ground).
Weight limit: the inventory has a max weight. You can't carry more than the max. The counter at the top tracks it.
There must be a manual overwrite where admins can remove inventory items from people.
Add tons of notifications for different scenarios (searched, pickpocketed, item stolen, dropped, picked up, inventory full / over weight, item lost on death, item lost from combat logging, etc.).