Is it possible to make changes to ebps extension templates?

I am in the editor trying to make changes to play around with a tuning pack mod that has different population caps for villagers and military. To do that, it seems like the easiest way would be to add a few rows to the existing extension template. Is this possible to do? It is greyed out:

Thank you!

Couldn’t you very well just up the max pop and restrict the max number of villagers able to be built?