Doors store a destination map and position. Most of the time, when the player changes maps, it is done via a door (or an exit door which returns the player to a previous position).
The game support additional index space for more doors, but there is no space for the door section to grow, so saga2edit does not allow doors to be added or deleted.
These properties control the destination of the door. X and y and measured starting from (0, 0) at the upper-left corner of the map. The preview will show part of the map that will be visible on screen after entering the door with a red X mark indicating the actual destination tile.
This controls the direction the player will be facing after going through the door. The corresponding exit door will have the reverse facing.
The game doesn't use this flag, but there is a code path associated with it. This appears to teleport the player without loading or reloading the map. However, this has not been tested in practice, so take care if using this option.
If this flag is set, the door sound will play when the player uses this door. The corresponding exit door will have the same setting.