Exclude full product template from synchronization
You can exclude specific product and all it’s variants from syncronization by setting this checkbox on the Product template form.
Exclude specific product variant form synchronization (advanced feature)
You need to fully understand what you are doing as this may lead to inconsistency of variants in Odoo and in the e-Commerce System. So be sure that this is desired behavior before using this options
If you go to individual variants of the products you can unselect checkbox for specific sales integration, just for this variant. All other variants will still be synchronized except this one.