There are a couple of steps in the editor:
1. Go to the General Tab and choose Deity.
2. Do a New (Copy) and pick one of the Pantheons, they should look like {bmp npcclass} Celtic Pantheon {bmp npcclass}
3. In the new copy, change the name and give it an ID as normal. Make sure you leave the {bmp npcclass} text alone, just change what's between them.
- Then go down to the Deity Category button and hit Edit . Choose - New Tag - and hit OK.
- At this point give it a tag unique ID like MYIDNamePN - where MYID is your personal user Identifier, in the Name field type the Pantheon like you would see it in the list (ex: Celtic Pantheon), you can leave the abbreviation blank - hit OK.
4. Hit the Diety Category Order Group button and select a tag, if you're worried about overlap choose a higher number, and write it down.
You now have the header for your pantheon ready.
For each diety, you'll do a New (Blank), to make a new diety.
Make sure you use the same Diety Category tag and Diety Category Order Group tag you chose for the header.
Note: The Header will not show up unless you have at least 1 diety for the pantheon defined using the same Diety Category Tag, so don't expect to see it if you try to test it before adding dieties to the category.