Can I have multiple listings of the same product on eBay?
Yes, if you have multiple eBay accounts on eBay.com, and/or accounts across eBay.com, eBay.uk, etc... You can list the same product multiple times across those different accounts and WP-Lister will maintain proper inventory based off sales across all those accounts. We should remind you that doing so may be a violation of eBay's "Duplicate Listing" policy.
However, if your objective is to list the same item multiple times on the same eBay account, then the only way to do that and have WP-Lister sync the inventory correctly is to create multiple products in WooCommerce and manually distribute the total stock between them. You can hide the additional WooCommerce products easily by setting their visibility to hidden.