Thanks for your offer of help.
Turns out it was post 44 and it does mention how to set the first waypoint if the bird hasn't moved:
1. Coordinates of the first waypoint can be used to set own coordinates after INS align completed
a) on HSI page choose wpt 0 using PB12 "up" or PB13 "dn", then press PB14 "WPDSG"
b) on HSI page press PB7 "UPDT", press PB7 "DSG", press PB6 "ACPT"
That did the trick for me, so all is good now.
My track is 32MB, which exceeds the file size limits.