In 6.3, Firepower introduced the following feature (but ONLY on Firepower Device Manager):
"The deployment window has changed to provide a clearer view of the pending changes that will be deployed. In addition, you now have the option to discard changes, copy changes to the clipboard, and download changes in a YAML formatted file. You can also name deployment jobs so they are easier to find in the audit log."
https://www.cisco.com/c/en/us/td/docs/security/firepower/640/fdm/fptd-fdm-config-guide-640/fptd-fdm-get-started.html?#task_BEE4E37389B64E518EE91FF3824476A9
Prior to that you had to manually undo anything you changed click-by-click.
Unfortunately in FMC we still have that limitation (even with 6.4.0.5). Hopefully 6.5 will offer the feature but we'll see...