There are a number of Harry Potter spells Hogwarts Legacy likely won't be able to use since they would not have been invented yet. The history of magic in the Wizarding World is long, harkening back to ancient times, but its uses are constantly evolving. Including Harry Potter himself, the late 1990s saw the confluence of many great witches and wizards, with Albus Dumbledore and Lord Voldemort perhaps the most notable two. Both pushed the boundaries of what is possible with magic, but there were a number of other figures who invented spells throughout the 20th century.

https://screenrant.com/harry-potter-spells-hogwarts-legacy-invented-after-canon/