I wanted to change “Refund Policy” to “Returns” but it took me a while to find out the answer so I thought I’d share it here.
It is possible to change the title that gets displayed. Head to: Online Store > Theme Name > Actions > Edit Languages. Then click on Checkout & System. The page is very long, but near the bottom you will find references to the policy pages, and you can rename them here. However, this only changes the title, not the handle.
I contacted Shopfiy Partner support to check if was possible. They confirmed that if policies are entered through Settings > Legal, the handles are set. The only workaround is to create a Page instead, but that won’t get pulled through to the checkout. This means that if you need to make any changes to the returns page, it needs to be changed in two places which isn’t ideal. So I think we’ll need to stick to a slightly inapproriate slug for the page for now.
The helpful person at Shopify submitted it as a feature request.