Edit available Blueprints in Add Dialogue

[ModernTrips]

Hello,
i have a blueprint with the pages preset from which i want to be able to create children of that page but only from one of my other available blueprints, see the image attached.
How do i write that in the parent blueprint?

[texnixe]

Try:

templates:
  - template_a
  - template_b

[ModernTrips]

thank you.