Bulk editing of your eBay categories is available for Published & Ready to Publish listings within the eBay channel.
To access the bulk edit tool, navigate to Listings, then select the the listing status, then select the listings that will share the same eBay category.
Next, select Bulk Edit and choose eBay category.
Search or select the eBay category and choose Continue
Edit the eBay attributes or leave them as is and select Update