The source – twitter.com
The Google Ads team is going to add account-level minus-word support for Performance Max campaigns. According to Jeannie Marvin, this is needed "for brand safety." No keywords will be added for such campaigns.
There are no current plans for a keyword tab in PMax. There are, however, plans to support negative keywords for brand safety at the account level. cc: @C_J_Ridley— Ginny Marvin (@GinnyMarvin) February 15, 2022