Hi Folks!
It’s been a few years since this was answered, so for anyone who stumbles across this thread here’s an update before an admin comes along an arbitrarily closes this post.
Since then, the function to remove from the native WIX shopping cart has been exposed in Velo. It is a promise, so handle with care.
cart . removeProduct ( cartLineItemId ) → You’ll get this ID from the cart. It’s close to a position id.
https://www.wix.com/velo/reference/wix-stores/cart/removeproduct