@CaptCanada
It depends…
When you have a simple one-flight mission like BARCAP, you can change it extremely without having to watch other flights.
The steerpoints timing will be flexible around the Take Off and TOT waypoints. You can even lock/unlock waypoint times. Though, if you stretch it too far, you will get too fast or too low speeds you can never achieve when flying.
But if you are a SEAD Escort or your Strike flight has Escorts / SEAD flights with you, changing the flightpath too much will take those advantages from you- ending up against MiGs without your Escort or against before unseen SAMs without your SEAD flight.
Though, you can try it, but also go into the ATO to change the waypoints of the related flights, too.
If you really want to edit such things yourself, get familiar with planning your own multi-flight packages. Memorize some noticeable points on the map and draw the steerpoints with every flight added. Let the one stable waypoint time be the Time On Target.