If you are trying to use the Scenario Editor for any Custom Tribal added by any mod other the the Core game you will get a tons of errors.

You can still play these, just not edit them. And It will just throw two harmless RED errors at start and the rest of the game plays fine.

If you wanna edit a Tribal Start just edit the one that comes with the Core game and change whatever you like from there. Race, Start gear, Etc..

(There is a small work around the error. Pressing the ESC key till the error log goes away then Click the Red X's to remove parts till you get past Short Bow and Pila, Will bring back the menu..)