How to extract Marlin configuration from compiled firmware

I recently bought an chinese A10 (not my first printer) "Recv: FIRMWARE_NAME:Marlin V1; Sprinter/grbl mashup for gen6 FIRMWARE_URL:[www.mendel-parts.com] PROTOCOL_VERSION:1.0 MACHINE_TYPEk"

It prints very vell, and it's PID's are perfectly spot-on, rather impressive , Esteps are good, everything in the config seems to be very well set up.

I'd like to move to latest Marlin, but keep those key settings, and maybe others - how would I proceed ?

You go back to the manufacturer/seller and demand a copy of the firmware source code. They need to provide it to comply with the licensing.

Other than that M503 will tell you most (but not all) settings (eg thermistor setting are missing)

No way to actually extract all settings other than getting the source code.

thank you.