The new feature that allow you to hide PayPal Express Checkout easily without touching the PayPal payment methods is available only for Shopify Plus members, so be sure to be a Shopify Plus member before to use it.
Let's see how easy it is now to hide PayPal Express Checkout.
From the dashboard create a nu customization
In the menu you can immediately see the "EXPRESS CHECKOUT BUTTONS"
The green specifies that this function is available only for Shopify Plus members and all the other will not have any effects by using it
Once you select it's time to set up the rule.
Tuggle the "PayPal Express Checkout", "Active" the rule and hit "Save".
Your rule now is active and on your store there is not any chance to use PayPal Express Checkout.