Katy here from Shopify. Thanks for posting. ?
Currently, there isn’t a way to exclude products from a collection by tag by default within the admin.
Though I will pass this feedback along to our developers as a feature request on your behalf.
While our our other forum users may be able to help you custom code this to your theme, the alternative option would be to work with products that do have certain tags instead, and remove these tags from the products that you would exclude from the collection.
Hope this helps you, Sam. Thanks again.
Katy | Shopify | email@example.com
Hey there – Just chiming in with our use case for excluding tags from collections:
We are getting ready to run our first clearance sale, and we created a "clearance" tag to assign products to this colleciton.
Across the site our product collections are organized by tags. Ex: products tagged "sweatshirts" are in the Sweatshirts collection, "tee shirts" in Tee Shirts, and so on.
We would like products that are put on clearance to be automatically removed from their default collections. Obviously, we can do this by removing their pre-existing tags. But it would be a lot nicer if we could simply assign the default collections to exclude products that are tagged "clearance".
Hello! We just developed an app for excluding tags from smart collections - https://apps.shopify.com/advanced-custom-collections
Hope this will resolve your issue. Please try it out and let us know your feedback =)