Thought I'd share this because I couldn't figure it out. To bulk edit promoted ad rates, go to Seller Hub - Advertising - Campaigns. Click on the current campaign and you can do a variety of things, including bulk edit the ad percentage, add listings, etc. There's a ton of great metrics also.
Why is this not in the regular Bulk Edit section? Anyways, hope this helps someone like me.
Thanks to @resellcny for the YouTube short showing this.
Best of luck selling today.
