According to the search results, Yuji Itadori does not have a domain expansion technique as of now. However, he has the potential to unlock a domain expansion due to his innate domain potential and the immense cursed energy he possesses. A domain expansion is an advanced innate technique that allows jujutsu sorcerers to manifest their cursed powers to the utmost limit within a metaphysical space created by sorcerers to enhance their cursed techniques. It is achieved by expanding ones innate domain with cursed energy while using a barrier to construct it inside a separate space. Only a handful of characters have shown the ability to utilize it so far, and it is believed to be the pinnacle of Jujutsu Sorcery.