I'm guessing this object is how you get Juni to shift screens seamlessly, as opposed to the "shift" blocks, which aren't so seamless.
Not really. Shifts and Warps have very different uses.
Edge Warps occur upon leaving a screen. Essentially, they change which screen each edge of a screen leads to. This lets you physically connect two screens in-game when they aren't actually adjacent in the map. It also lets you make a screen wrap around itself, like you see in that video (by the way, yes, that does use Edge Warps); all you have to do is make the screen edges Warp back to the current screen.
Edge Warps can be set up in World.ini or in KSManager, your choice. Then once you place a Warp object (the thing you're asking about) on the screen, the Edge Warps will start working.
There's also another kind of Warps: Flag Warps. Those occur when the player enters a screen, making the player end up elsewhere if certain conditions are met.But it's quite different from shifts.
Warps occur in-between screens, connecting areas.
Shifts are a part of the action, teleporting the player when activated.
Shifts and warps are both optimized for cases where the player ends up in the same screen: the screen won't be reloaded. This is why the Warps in that video are so seamless; they keep you on the same screen.
If you made a Shift that pointed to another place
on the same screen, you would find that it is just as seamless, because the game doesn't have to reload the screen.