How to add new custom parameter while creating new target audience

Hi @shivanim 

You're getting this message because the newly parameter not yet exist. So just to check where you need this parameter. 

In case you need this parameter at the time of page load (_view_ / target-global-mbox ) event then you simply add this in your target request. 

if you're using Web SDK then you can do this through sendEvent() method / if you're using at.js then you can use targetPageParams() and once this call made - the newly parameter will be available. 

you can check this document to send parameter in both approach. - https://experienceleague.adobe.com/en/docs/platform-learn/migrate-target-to-websdk/send-parameters 

Thanks