You can set up a Product CSV export with EZ Exporter containing only products/variants that belong to a specific collection or set of collections using Custom Filters.

In the Data Settings, set a Custom Filter like this:

• Collections Titles contains Best Sellers

This will include only products/variants part of the "Best Sellers" collection in the CSV export.

You can also combine multiple filter conditions so you can export products that belong to any one of the multiple collections you have set up.

For example, let's say you have multiple collections called "Best Sellers", "On Sale", and "Limited Offer" and you want to export the products and variants that belong to any of these collections. You can do so with these Custom Filters:

Data must match: any condition

• Collections Titles contains Best Sellers
• Collections Titles contains On Sale
• Collections Titles contains Limited Offer

Notes:

• You normally want to use the "contains" operator when filtering based on collections as a product can belong to multiple collections. You can filter by the collection ID or collection handle as well.
• Filtering collections at the variant-level is not yet supported, we're waiting for Shopify to update the API to add bulk querying at the variant level.