...
The tile model itself does not contain the door object itself, naturally, so you must leave a gap for the door you are going to add
It's critical in the tile model that the walkmesh must be If you wish to be able to walk through a door without using a transition then there must be a walkmesh at the creature' s feet and there is complete clearance above, regardless of how high the actual door is going to be. So leave a gap. It must be open if you expect a creature to walk through to select it. You don't want to obstruct a creature
This is theway Bioware/Beamdog do it. I have found that it's a lot simpler not to allow a creature to walk under a door at all, except if you use the door to connect two tiles
Note: this entry only be required if you want to set the resref on the door to your specific value by default (something that can also be done by editing a copy of an existing door entry).
...