@ezhka: It’s not about rule duplication (and understand your concern), it’s about first duplicating it, then changing the duplicated rule (URL and rules, minor adjustments) to create the rule-set faster. If a developer/webmaster has many websites to create/mod, then this feature becomes very useful. Also, if the suggestion is accepted, back-end codes will have to be implemented to ensure that if someone duplicates a rule then saves it without changes, Cloudflare will “flag” the condition with a proper message to the user (e.g., “Cannot use duplicate rules”). Hope this helps!
Now, how about some "votes’!