Do Not Edit Custom Audiences on Facebook
If you’d like to edit a custom audience created with CAE, please do not edit it on Facebook!
Only edit custom audiences using the CAE plugin.
Editing your Custom Audiences on Facebook could compromise them since Facebook’s does not support editing custom events data created from Facebook’s API.
If you have already edited one on Facebook, don’t panic. Just create a new Custom Audience equivalent to the old one using the CAE plugin and you’re set, you won’t lose anything from your custom audience.