In this reading, the nominative adjective pertains to Allah, the Lord of the Throne.

ذُو العَرْشِ الۡمَجِيدُ

In this reading, the genitive adjective pertains to the Throne.

ذُو العَرْشِ المَجِيدِ

Abū Jaʿfar al-Madanī

Ibn ʿĀmir al-Shāmī

ذُو ٱلْعَرْشِ ٱلْمَجِيدُ