Well, i have some time playing with D3 Edit and i've made some simplistic levels.
However, i have this doubt.
How can i add multiple Single-Player starts to work like in the Single Player Campaigns: When you die, you start in the nearest place from where yo died.
You add waypoint objects where you want the player to respawn after dying. They used to be on the Sound bar; OtherOne moved them to some other toolbar -- object, I believe -- in one of the "beta" builds. Once the player passes a waypoint, they respawn at that waypoint if they die.