You can turn the activity participants list in the engagement on or off. This enables or disables participants to see a list of all other participants taking part in this activity.
In order to adjust this setting, navigate to your event, then to the Activity Management module, and to the Engagement settings submodule.
Now expand the Features used section, and toggle the Participants list switch on or off, depending on your needs. The switch being on means that participants are able to see the participants list in the engagement app. Remember to click Save when you're done to keep the changes you've made.