Collection level feed settings
Collection level feed settings is one of the components that compose Effective feed settings, which is used to generate the final product feed.
It is accessible from the product group editor page, clicking on each of the collections to show the custom feed settings dialog.
Collections can be involved in a feed group in 2 ways: included collection and modification collections (or excluded/customized collections)
Included collections define the set of the products being included in all the feeds of this group. "All products" is a special collection that include all products in store. All included collections can have collection level feed settings.
Modification collections are added either to define exclusivity, or feed settings customization. In the screenshot, the Dogs collection is to define exclusivity (the group will include All products, excluding products from the Dogs collection), with collection level feed settings disabled.
Click on the Dogs collection to bring up the collection level feed settings form. With at least one settings, the Dogs collection will become "customised" instead of "excluded".
You can customize the title, description, Google programs, ID, and other attributes for that collection.
Settings at the collection level take precedence over the feed level settings, but less priority than product level feed settings.
Custom collection data
There are times you might need to pass down data from a collection to its products. This can be done using custom collection tokens.
The idea is to put the data into the custom data tokens (Custom data 0 - 3).
Then the data can be pulled using the corresponding tokens in feed attributes
Then the feed attributes will show up with the collection data