What is a filter?
Filters are groups of items from automated catalog, similar to Product Sets in DPA Catalogs.
Aside from launching Automated campaigns based on the Filters, you can also request an Export for a Filter from Studio.
How do I create a filter?
Open the automated catalog where you need the filter
Go to the Filter section
Click on the "+ Create Filter" button
The first section is the same as creation of Product set in DPA catalogs.
The second one is specific. From there you can choose how do you want to sort your items.
You can also use Google Analytics metrics for sorting.
Another thing you might notices is the max number of items. In Automated Catalogs, in most cases, one item equals one ad.
The limit that you see here is to limit you to the max number of items that you can launch in the same Campaign.
When you save the filter, save the catalog as well so the changes can be synced.