In this video, I go over exactly how I use Performance Max campaigns to improve my search campaign results. The secret is harvesting the search categories that are shown in the Insights tab and recycling these into your search campaigns as new keywords and ad groups.

In my opinion, these are better than the keyword research planner as they are much more specific than what is shown in the keyword planner. A bonus point is that you can also recycle these into the search themes of your Performance Max asset groups to improve the targeting of these further.