How to unify the origin of the NED coordinate system for all UAVs in a multi-unmanned system?

In multi-unmanned systems, it is very necessary to unify the origin of the local coordinate system for all UAVs.
The origin of the local coordinate system is the home point, and I think we can achieve the unification of the local coordinate system of all UAVs by setting the home point of all UAVs to a value of the same latitude and longitude height in this way.
However, I have verified using mavros, gazebo, and in fact this solution does not work. I can check the telemetry information of UAVs in QGC, and the result shows that the home point has been changed successfully, but the position information of local_ned is not changed, which means the origin of local_ned is the takeoff point of UAVs instead of home point?

No, it means the EFK_origin is different from the home location. What you want is to force the EKF_origin to a global unified value, and AFAIK that is just not possible.

Yes, the origin of the local coordinate system is indeed EKF_origin.
However, I think there is a way to change the EKF_origin, right? Because Mission planner can set EKF_origin

Mission planner and other GCS have a function to set the EKF origin.
However, in ArduPilot currently the EKF origin can only be set in non-GPS modes such as when using visual odometry and only one time.

There is a pending PR that could be amended to remove that restriction.

Though I do wonder if what you describe is truly necessary? Why must they be unified?