Probably you know you can wear more than one item at the same layer (alpha,tattoo...) but in case you didn't notice this feature here is how you can do it.
In the example we wear two alphas, right mouse click on the first alpha and click wear (or double click to wear), to wear another alpha make the same but choose Add instead of Wear. You can do it with any object or cloth.
The Inventory Context Menu is also useful to edit objects, have you ever had a problem selecting an object that went inside the avatar? or maybe you tried to select an object and the hair or any other object didn't allow it?
With the object worn, right mouse click on the object and select
Edit.
And now you can move it outside the body or anywhere you want.