You can have multiple Designated Contacts and should have more than one - for back up. Also one person should be a Primary Designated Contact, that person can administer permissions for the other DC's. You don't want too many people to be DCs - so that you maintain order in the communications/request etc.
Create and Manage Designated Contacts on Salesforce Help
https://help.salesforce.com/s/articleView?id=000334527&type=1