The 19-year-old has been added to the club’s B-list for the competition which can be updated ahead of every match day.
Galbraith is already a full Northern Ireland international and made his United first-team debut last season as one of the many youngsters who featured against Astana in Kazakhstan in November 2019.
The young midfielder was also included in the Europa League squad for the knockout stages in Cologne last year and was the subject of loan interest from League Two clubs last month.
Now heading into his fourth year with United the club have already made moves to retain him in the long run, agreeing a new deal with Galbraith last October which will keep him at Old Trafford until 2023, with the option of an additional year.
Fellow academy star Shola Shoretire also remains on the B-list after he travelled to Turin for the first-leg victory over Real Sociedad last week.
A brace from Bruno Fernandes as well as goals from Marcus Rashford and Daniel James earned United an impressive 4-0 ‘away win’ in the first-leg which was played on neutral ground.
Galbraith played the full match for United’s U23 side as they lost 3-1 away at Everton on Monday night.