This idea has been merged into another idea. To comment or vote on this idea, please visit ARISPMIYU-I-51 Enhancements to the Calculate new columns (on going).
If you have an existing complex calculation and wants to create a new one, it would be helpfull/time saving by using/starting with a copy of an existing one. Also for playing around/adoption of a column without harming the working one.
Thanks for filing this idea. We plan to provide this feature in the 2022May release.