I would put them on a global layer which acts like a HUD and remains between layouts, so where you create the objects (layer 0 in the tutorial) give that layer a global property and make sure in the other layout you have the same named layer.
Another option is to make the inventory and objects you can pick up 'global objects', checkbox on object properties, which accomplishes the same thing.
Also if you happen to mean a design something like going to another layout then returning to an 'inventory layout' so the inventory is always in one layout then there is something called Persist behaviour you can put on the objects which means the inventory will look the same when you return.