Yahweh causing Eliakim's authority to be strong and secure in the king's palace is spoken of as if Eliakim were a peg and Yahweh will set him firmly in the palace wall. (See: [[rc://en/ta/man/translate/figs-metaphor]])
Here "seat of glory" represents a place of honor. Alternate translation: "Eliakim will bring honor to his family" (See: [[rc://en/ta/man/translate/figs-metonymy]])