Way Point with timestamp (change speed dynamically)

Hello!

I wanna add time information for waypoints.
For example,

waypoint_1
lon=xxx1
lat=yyy1
alt=zzz1
time=0:00:00

waypoint_2
lon=xxx2
lat=yyy2
alt=zzz2
time=0:10:00

I want the speed of the craft to alter to reach each destination GPS Coord dynamically at the specified time.

If I should write a custom function, how do I write it and where directory do I should write it in? (Firmware or mavlink/qgroundcontrol, either or both?)

from…
Time Stamped GPS Coordinates