1° Select your main landscape
2° Activate Landscape edition mode
3° Select Manage and Add
4° Add as many tiles as you wish, they are seamless and appear as streaming proxies under the main Landscape actor
5° Save your one and only map and all added landscape tiles now appear in the world partition window
This is much simpler than creating levels and moving them by hand in world composition.
Note 1: there is a bug when sculpting over tiles, the smooth tool sometimes creates huge holes. ctrl-z is in order.
Note 2: Once a tile has been added to world partition, I couldn’t find any way to remove it. From the “Landscape editing mode → Manage → Delete” I can remove tiles but they still appear as Landsceape Streaming Proxies and still appear in world partition.
Note 3: UE5 will create a folder “ExternalActors” inside the content folder which will contain subfolders for all levels you have ever created or even deleted in the project. Still obscure how to deal with that, probably responsible for deleted parts of the world partition to still show up after being deleted with the landscape tool.