Slimeling Inventory Bag
The Slimeling Inventory Bag is a chest that can be equipped on Slimelings.
To equip the Slimeling you own, right-click it. In the Slimeling window click on the Chest icon, place the Slimeling Inventory Bag in the lower slot available. Now you can place items in the bag.
If for any reason you remove the bag with items in it, all items will be dropped.
This video (from 5:03 to 5:20) depicts the use of the Slimeling Inventory Bag.