In this version of the system you can show temporary meshes in equipment slots, even if something is already equipped in it. The showTempMesh function on the AC_Inventory_System component lets you define the ItemRowName of the item mesh you wish to show, the MaxDuration (number of seconds) to show it for, the EquipmentSlot and EquipmentSlotIndex to show it in.
The MaxDuration is used with a timer to hide the temp mesh, you can however manually call hideTempMesh to revert the state on demand.
In the demo world when we consume an item, we show the mesh of the item in our hand while we play the animation to consume it. This is done using this showTempMesh function.
This might also come in handy if you have an RPG styled gathering system where you wish to show the gathering tool while performing the animation to gather, without having to actually equip the gathering tool.
This temp mesh system is pretty basic, and was a last minute addition to add some more polish to the consumable examples. A limitation of it is that it is only set up to show a single mesh at a time. If you need to expand on this to show multiple you can find everything related is handled inside the equipment component, search the blueprint for temp to see the related methods and variables.