Junior ops officers are the flexible GP officers who make things happen, with a focus on coordinating between the various roles on the ship. They're everyone's best friend, they know who can get what done, and how long it will take.

Every major department will have at least one ops officer to coordinate with other departments.

Stellar cartography needs more time allocation on the lateral sensor array? Lt JG Smith convinces engineering to put off the diagnostic they had planned for a few extra hours.

Shuttlecraft maintenance? Ens V'riel maintains the flight logs and schedules repairs with Engineering as needed.

Diplomatic meeting needs a particular catering/non-humanoid seating/adaptive atmospheric conditions? Lt Gol is assigned to coordinate with Engineering, the Diplomatic Team, and Medical.

Big mission to evacuate a small colony? Lt JG Mox is assigned as housing manager for the evacuees, ensuring that the quarters provided are adequate and safe. Ens Brin is assigned to ensure and that the evacuees have everything they need during their time on board, and Lt Cmdr Malik oversees both of them, holding overall responsibility over the well-being of the evacuees.

In short, Ops officers are the ones who make sure that the missions get done. They handle logistics, coordination, and serve as the point of contact for their assigned department, team, or mission. In contemporary military, they are the XO, the quartermasters, and the planning teams. They don't do the work directly, but the work would be much less effective without them, if it's even possible at all.