How to add new building options on the Villager Grid Building TAB?

I want to add new building options to English Civilization as I will get some buildings from Norman Civilization from the campaign.

On the picture I attached above, you can see the X marks for the empty Grid slots when you click on villager to choose a building option.

In Content Editor, I couldn’t find how to add new building options to add on the villager grids TAB.

If anyone knows how to do it, please would you guild me? thank you very much.