If the Adventurous Journey is planned as an activity through the Programming function of Scouts | Terrain, then yes absolutely youth members can have a Participate, Assist or Lead credit added to their Achievement Pathways, once the Adventurous Journey activity has been concluded in Scouts | Terrain.
This involvement will credit where applicable to their Milestones.
Please Note:This site is for the use of Scouts and Leaders who are implementing the Scouts Australia new youth program. It is not relevant to members who are still operating on the old program.
You're most welcome to still have a look around, however!