Originally I deleted an Azure AD B2C directory, which according to the MSDN guide included removing the b2c-extensions-app. When I thereafter created a new Azure AD B2C directory with the same name, the b2c-extensions-app was not created automatically.
Following this, I tried to create a new Azure AD B2C directory with a different name, which also missed the b2c-extensions-app.
How come both of them misses the b2c-extensions-app? And what can be done to fix this?
EDIT:
To answer the second question. When creating an Azure AD B2C directory the b2c-extensions-app might not be created right away. In my case it appeared after a while, which can be good to know.