Check "Destroy on startup" in the Attributes section of the object's properties.
Then when you need to create it during run-time, use the System action "Create object."
Oh, you mean you don't want them cluttering up the layout itself while you're working in the IDE? I dunno. You'll just have to stick them somewhere. You could always just use the Hide feature if they're in your way or whatever.
The "Hide Selected" option appears not to be working (it's grayed out). But the "Hide Unselected" and "Unhide All" are working ok.