A friend of mine sent me these eleven places where the 1611 KJV has textual critical notes, places where the translators or editors felt it important to tell readers when the Greek New Testament manuscripts to which they had access included variant readings. Such notes are not a new invention.
(NT examples HT: Andy Efting)
As best I can tell, having checked David Norton’s New Cambridge Paragraph Bible, there are four places in the Old Testament (1 Chron 1:6, 7; Ezra 2:33; 10:40) and two in the Apocrypha (1 Esdras 5:25; 8:2) where the KJV translators did the same thing.