Calendars only Collections accounts, shows under 'Edit' in addition Contacs and Mail
File → New → Collection account, emal address firstname.lastname@example.org → Lookup → Next. Select Collection → CalDAV, remove the selections for Mail Receive, Mail Send and Collection → CardDAV. Next → Finish.
Edit → Accounts → [select email@example.com] → Edit. It shows all of Email, Calendars and Contacts, but should show only Calendars.
I do not know what the purpose of the Edit button is, but in 3.38.5 its implementations is mystical.