Complex sentence: The post is currently held by Carolina Barco Isakson who is soon to leave her post being replaced by Gabriel Silva Luján who has been appointed but has not yet presented his Letter of Credence.
Split into simpler sentences: The post is currently held by Carolina Barco Isakson, who is soon to leave her post, being replaced by Gabriel Silva Luján. He has been appointed but has not yet presented his Letter of Credence.