As far as I understand, you need to enable subsection prerequisites in the course advanced settings:
Then, the prerequisite setting will become visible in the subsection advanced settings:
Note that the “common-env-features” is a JSON-formatted patch, so booleans are written as “true/false” (in lower case) and not as “True/False”:
name: milestone
version: 0.1.0
patches:
common-env-features: |
"MILESTONES_APP": true