Can we still edit the UTM link?

No !

Once your utm link has been added to the tracker link section and your campaign has been saved, you cannot change the utm link.  Even if your campaign is unapproved. 

The trackerlink (utm) is saved when the campaign is initially created.

NOTE:- Its best to delete the campaign and create a new campaign with the right UTM links, as the links are generated at the time the campaign is created.