enabled property
Enabled is the admin lever. Absent reads as ON, so only an explicit false turns a phase off — and it takes every step filed under it out of the journey, not just the heading.
Please note: This property should have been non-nullable! Since the specification file does not include a default value (using the "default:" property), however, the generated source code must fall back to having a nullable type. Consider adding a "default:" property in the specification file to hide this note.
Implementation
bool? enabled;