Why Can't we add value list as exception for Threshold rules and correlation rules even in 7.12?
Hey there @tushar.bansal 
Please see this comment for why Value Lists can't currently be used with Correlation and Threshold Rules. And here's an enhancement request for adding Value List support to Correlation Rules if you would like to
to better help prioritze.
In the interim, we've updated the documentation to clarify this.
Thanks! 
Garrett