It's interesting how new products come out and they lose key features that old products excelled at..
ASDM was excellent at allowing the preview of configuration changes when you went to apply them or choose to discard. How is it that this feature is not already enabled in FMC (Firepower Management Centre)? It is great that we can now see a somewhat detailed list of what is going to be deployed by FMC but we need more flexibility in being able to cancel a piece or full change at the deployment spot.
I guess the difference may be just the complication of FMC allowing changes to be saved and not deployed prior to closing the browser session but I personally find it full of risks and requiring too much review since the changes you might need to deploy for an emergency could also contain changes that are just planned and not ready for execution yet from a different administrator.
FlexConfig listed as a work around is a bit insulting... Hopefully this feature enhancement gets lots of attention and included in a new software release.