Thanks again for getting back to me Ken, most appreciated.
I'll take you through my previous workflow which I'm aiming to replace with SGP. I image 100% mobile and setup before imaging. Between the *'s is what I was hoping to be able to replicate with SGP, I have everything but the syncing working (obviously ).
Polar align (Slew and Drift with PHD)
Slew to target using CDC or similar.
Capture and platesolve using AstroTortilla on current target, with "Sync scope" and "Re-slew to target" enabled, (Usually through a few iterations).
It's the capture, sync and re-slew without having to manually transcribe the "ASCOM reported" position of the mount that I'm trying to integrate into the SGP workflow. I'll re-iterate that I'm new to SGP, so the feature request for the button was based around the "ad-hoc" use of planetarium SW then the syncing of the mount and plate solving to correct the pointing error from cold start on a mobile rig. I thought that using the SGP plate solve engine after populating the target field would be one way to achieve this.
So to answer your question "How do you normally sync your mount's position with the sky?" Via AT's integration with BYE and platesolving, and was hoping to use SGP's plate solve to achieve this somehow.