Manage Spawn
This menu allows you to manage all the different types of spawn for the world or realm.
Set Default Spawn
Clicking this will set the vanilla world default spawn to your location.
Set Custom Spawn
Clicking this will set a custom spawn at your location, rotation, and head rotation (where you are looking).
The Default and Custom spawns are used for the Spawn button in the RMT menu. If a custom spawn is not set, the default spawn is used.
Set First Spawn
This option is to set a custom first spawn where new players will spawn. Clicking this will set the spawn at your location, rotation, and head rotation (where you are looking).
If you have a Custom and/or First Spawn, then buttons for each will appear at the bottom to delete; clicking these buttons will delete the selected spawn.