No, the gift product will not be shown in the order details during checkout or marketplace invoice since GWP promotion is a non-integrated promotion with marketplace.
For e.g. if user has create a GWP promotion in SelluSeller Buy product X and get product Y free. So when customer buys product X on platform the order gets sync in SelluSeller and SelluSeller will add product Y in order during promotion period. Customer will not see the free gift product on marketplace order details/invoice.
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