You can trash products with a CSV using the status column. First, you have to enable the status column in Catalog Settings > Product CSV:
Once enabled, you can set any status for each product:
- publish – to publish the product immediately
- future – to post the product automatically in the future (you also have to select the publish date to make it work)
- draft – set the product as a draft
- pending – Awaiting a user with the publish_posts capability (typically a user assigned the Editor role) to publish
- private – set the product as private
- trash – to move product to trash