Unfortunately, we do not have a bulk delete function on Poshmark. This applies for bulk deletion of For Sale, Not for Sale, or Sold Out Listings.
If you have a bulk batch of For Sale listings you'd like to move to Unavailable, we recommend leveraging either our Bulk Upload file or API inventory feed to 0 out the inventory for these SKUs. This will turn the listings to Sold Out. Once you share available listings, this will cause the Sold Out Listings to drop to the bottom of the closet (since the closet is sorted by default using the "Just Shared" sort order).
You are also able to manually move listings individually to Sold Out or Not for Sale states via the standard listing creation flow in-app. Listings with active offers on them cannot be turned to Not for Sale until the offers expire, so if you'd like to move them to be not-purchasable, we recommend that you 0 out the inventory to Sold Out state instead.