A co-admin should be able to manage the whitelisted domains for external sharing which is currently only possible by the main admin. Similarly for Shield alerts, only an admin can currently unlock a file. Whilst an admin should be the only one able to change the set up, decide on the alert settings etc a co-admin should be able to manage existing alerts. The lack of granularity of what a co-admin can do makes it difficult to manage as the only alternative is to give co-admins full access to config which isn't a viable option.