Help with using Portal Editor on Overworld

[ArchProctor]

Say I want to go to an overworld map that didn't previously have a warp, and I build a mound with the warp pit (or use object FC, I've tried both) and put down sprite 61 over the pit. The sprite is located at (6, 4) on all the maps that already had a warp, so I put the pit and sprite there just to be safe. I set the destination. In the game I see the little portal floating above the pit, so I send Link to what I assume isn't his death by going down the pit. I just get hurt and respawn; the warp didn't do anything. What could I be missing here?

[Fatories]

I have not a clue. I tested it myself and it appears that only the maps that contain warps originally can be edited to warp to new maps, but I could have sworn that wasn't the case.