This post was originally published on June 13, 2019 as a stand-alone post and detailed how to exclude placements in Smart Shopping Campaigns. However, because Performance Max has now Tae-Kwon-Doed SSC to death, we're releasing this updated guide as to how you can exclude placements from Performance Max campaigns.
If you want to know how to SEE placements in PMax, check out this walk-through article (it's not complicated!): How to Find the Placement Report for Google Performance Max Campaigns.
Step by Step Guide for Excluding Placements in Google Performance Max Campaigns:
Step 1 :
Navigate to the Account > Content > Exclusions tab in the left hand nav, as seen here:

Step 2:
Select the Account Level. Please note, these can only be applied at the MCC or Account level, you are unable to apply campaign level placement exclusions to Performance Max campaigns.

Step 3:
Add the app categories or placements you would like to see excluded from ALL Display and PMax campaigns in here and you're good to go! At least, we hope so... according to Google you should be good to go.

Finally, a big thanks to Bob Meijer for pointing us to this on LinkedIn!
_____________
If for some reason, you want to view the original post How to Exclude placements in Google Smart Shopping, then read below.
_____________
How to Exclude Placements in Google Smart Shopping
You can read the previous 3 posts here: What Is Smart Shopping? – Part 1: The ZATO Guide to Google Smart Shopping Campaigns
Establish Your Strategy – Part 2: The ZATO Guide to Google Smart Shopping Campaigns
Should You Switch From Standard Shopping Ads to Google Smart Shopping? – Part 3: The ZATO Guide to Google Smart Shopping Campaigns
Just yesterday, we at ZATO discovered and shared that you could see placements in your Smart Shopping campaigns through the API. I lamented in that post (here: How to See Placements in Google Smart Shopping Campaigns ) that we couldn't add them as exclusions. Well thanks to a line of questioning on Twitter (Thanks Emma, Dan, Andrea, and Liam!) and then our own experimentation, we have learned that you can actually add these in as Account Level Placement Exclusions! To SMART SHOPPING campaigns! Google's Black Box obtains a small chink of in its armor of manual optimization (*gasp*).
Here is how you exclude placements in Google Smart Shopping campaigns:
(1) Navigate to (or create) a Smart Shopping Campaign of your choosing.
(2) Discover which placements or mobile apps you need to exclude from your Google Smart Shopping campaigns.
Use this helpful walk-through we created for seeing this data: How to See Placements in Google Smart Shopping Campaigns.Video re-shared for your convenience, transcript and screenshots in link above.
(3) Select the Placements tab.

(4) Select the Edit Icon and change the Dropdown from "Campaign" to "ACCOUNT".
This is very important, because you cannot add placement exclusions to Smart Shopping campaigns at a Campaign level! Why not, you ask? Who knows.

(5) Select all the Youtube Channels, Videos, and Website Placements that you want to exclude and get going!
Don't forget two of our favorite exclusion lists to add to every account:
- Seer Interactive's Top Display Placements to Exclude
- Joe Martinez' Kid Videos to Exclude on Clix Marketing
Thanks to those who got us digging in to uncover this! I'm PPCKirk, and I'd love to connect with you on: Twitter & LinkedIn.
Smart Shopping Training by PPCKirk
Psssst, hey! Want to keep learning about Smart Shopping? Check out PPCKirk's Udemy course, jam-packed with 5 hours of exhaustive content on everything from feed tips, to SSC structure, and ad creative recommendations. It's the kind of thing people pay lots and lots of money for, but we're selling it for $69.99. It also comes with exclusive access to a private Shopping Ads Facebook group where you can discuss Shopping Ads with your classmates, and get questions answered directly by Kirk himself. Grab the course now!