To sell certain products only via the POS App without also offering them in your online store, these products must not be available in your main shop. To do this, simply remove the main shop category in the Categories tab of the product master data, in the Assigned Categories section. If the product no longer has any category assigned at all, that's also fine, since it will still be available for purchase via the POS App. Categories can be created and edited under Products → Categories.
Alternatively, you can also deactivate the product by removing the checkmark next to Active in the product's master data. In the POS App, this product will then be shown as deactivated, but it can still be sold as usual.
