You can test out the vendor experience by adding yourself as a vendor in your Shopify admin, then send yourself an invite through your ConsignMint dashboard. (Be sure to use a different email address than your Shopify account.)
Then you can log into your vendor dashboard and take a peek around. You can even try out the product submission process. Just remember that approved product requests are made live on your shop, so you'll want to delete any approved test product(s) from your Shopify admin.