A registration can't be cancelled or changed from your account: the organiser manages their entrants.
Cancel
Contact the organiser from the event page or their public page. When they cancel your registration, your spot is freed for another dancer and your ticket shows as Cancelled.
Change category or fix a detail
Same thing: ask the organiser. Editing your ShadowPass profile doesn't change a ticket that has already been issued.
Refunds
ShadowPass doesn't collect entry fees: any refund is handled directly with the organiser, under their own terms.
In a team? A member can leave the team themselves from "My tickets".
→ Manage my team
The "Clean up history" button in "My tickets" doesn't cancel anything: it only removes
tickets for past events from your list.