If you're creating or editing a large number of dynamic search ads and targets, use Search Ads 360 bulksheets instead of the Search Ads 360 UI.
Note that you'll need to use the Search Ads 360 UI to set up a campaign for dynamic search ads, or to change the web site or language you've specified in a campaign. Once you've done that, you can use bulksheets to create or edit dynamic search ads and targets.