Chief diplomat?

Question

what is it? and how migh the president be it?

Answer 1

The Chief Diplomat is the Ambassabor and in his absence, it is the Consul.

Answer 2

In regard to the US:  The Chief Diplomat conducts foreign policy by directing the actions of American ambassadors and others in their place.  It could easily be a presidential role, or be delegated.

Note:  The Chief of Mission is the ranking officer in an embassy, permanent mission, legation, consulate general or consulate (i.e. the ambassador, when present, at an embassy, or the Chargé d’Affaires when standing in).