It is possible to specify which participant fields are visible for planners for certain events.
to set the fields invisible, select the event you like to make the specific fields invisible.
Within the even select 'Fields manager'
Select the fields you like to make invisible to the event planner by ticking the box in front of the field
Select the 3 dots behind fields and select 'Set field Visibility'
When going to Participants, the selected fields should not show up anymore.
To make the field visible again, select Use in the Event
The selected field should now show up again under the participants.