The seamless teleportation feature is a feature that makes the teleport between games in a universe look seamless. This feature currently isn’t available to developers because it was made during the hack week at Roblox but sometimes hack week projects do become real features, don’t get your hopes up though.
There currently isn’t any way to make seamless teleports between places. I would suggest you make a feature request in #platform-feedback:engine-features explaining your use cases and why you want a a feature like the one shown in the video.
I personally really want a seamless teleportation feature because I can think of many awesome use cases.
If you are interested here is a thread going into more detail about this feature: