What a manager can see in a learning journey comes down to one thing: which participants they're connected to. There's no per-activity or per-field privacy switch, so "limiting" a manager is really about who you connect them to — and whether a manager is the right role for that person at all.
What a connected manager sees
A manager who's connected to a participant sees that participant's full activity in the journey — their answers, reflections, and submissions, not just whether an activity is complete. Being a manager doesn't make them an admin: they can't edit the journey, and they can't see participants they aren't connected to. Their view is scoped to the people assigned to them and nothing wider.
There's no setting that hides part of a participant's work
If a manager is connected to someone, assume they can see everything that person does in the journey. There's no toggle that keeps specific activities, answers, or submissions private from a connected manager. So the way to control what a manager sees isn't a visibility setting — it's the connection itself, and what you choose to put in the journey.
How to actually control it
Only connect a manager to the people they should support. A manager never sees participants they aren't connected to, so you control their scope through the manager assignments on the People page. See Adding managers to a learning journey and Changing or removing a manager mid-journey.
Keep anything a participant wouldn't want their manager to see out of that journey. Since a connected manager sees their employees' full work, design the journey assuming that visibility.
For a view-only stakeholder, use a team guest instead of a manager. If someone just needs a broad look at the journey — a second-line manager, a sponsor, an observer — and shouldn't be anyone's manager, give them team-guest access. A team guest can browse the learning journey and its statistics without getting the per-employee manager view. See what a team guest can do and when to use one.
For two roles that need different views of the same people, run two journeys. If a line manager and a mentor should each see different things about the same participants, set that up as two learning journeys with the same participants, one designed for each role. There's no way to give two managers different visibility of the same person inside one journey.
Before you rely on it
If the boundary matters, preview the manager experience before you launch — that's the surest way to confirm a manager sees only what you intend them to. See The manager's experience in Knowly.