You will need to come up with a system of waypoint management that works for you ...

If you export waypoints from unit A and import those waypoints into unit B on Monday ...and then on Friday export waypoints from unit A and import those waypoints into unit B ...

You now have duplicates of all waypoints up thru the previous Monday on unit B ...
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There is the option in the Waypoint Management menu to organize the waypoints by "Newest" and then select just those new waypoints to export from unit A ...but you have to keep up with when the last export was so that only new waypoints are exported ...

Rickie