Ginny Marvin, the Google Ads Liaison said on Twitter that there are no plans for a keyword tab in Performance Max campaigns but there are plans to support negative keywords for brand safety at the account level.
This news comes after Chris Ridley shared a screenshot on Twitter of his Google Ads representative's screen. Chris said "My Google Ads rep has just screen shared with me while viewing my PMax campaign and I can confirm they have a "Keywords" tab within the campaign. See attached images showing the same PMax campaign." Here is that screenshot:
Ginny Marvin responded to this saying "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."
So more to come for performance max campaigns in Google Ads...
Forum discussion at Twitter.