To create an event where only the lead is required to attend, such as a "Shadow Day" for students (e.g. 'Try year 7 for a day'), head over to the Forms tab at the top of the page and edit the form associated with your event.

Below the Parent/guardian collection field, hover and click on the Attending checkbox:

Here you can choose to set the Default option of if the attending checkbox on the form is Checked or Unchecked.

You can also select Show this field, which will toggle the visibility of the attendance checkbox on the form.

For example, for a lead-only event you want to uncheck the Show this field and the Default option as Unchecked. On the form, the guardian wouldn't have an option to set their attendance and in Funnel they would be marked as Not attending.

Once you're happy with your changes, don't forget to Save and Publish.