Build a new release of Marlin

I’ve previously built Marlin for my Ender 3 Max, and have been using it for a while.
I want to re-flash the printer, but would like to update to the 2.1.x release.
Does anyone have experience upgrading Marlin versions on a build?
Can I just copy over top? Do a completely new build?


My approach is to copy in the later version of Marlin into a new folder and then do a kdiff to look at the differences in the configuration files and make changes where appropriate to maintain my settings.

My concern was that I would lose some important setting when doing the new version.