I've heard too many stories of folks experiencing a accidental discharge when decocking manually.
There have also been instances of accidental discharge when carrying Cocked and Locked, when the Safety Lever gets accidentally bumped to the OFF position.
With Firearms Handling in General, you can never be too careful.
Manually decocking a handgun, particularly back in the Revolver Days, both SA and DA, used to be considered an essential skill.
If one is to carry a Cz75 pattern Pistol with a Loaded Chamber in the DA first Shot Mode, then that skill must be learned, safely.
My personal practice is to go outside to my back Patio, point the Pistol at the dirt, rack a round in, then manually decock the Pistol.
https://youtu.be/XO59J7tBKuMI've been using the "Over the Top" method shown above, without incident.