Please contact support directly for this. It only takes our team a few moments to transfer it over.
You can see the options for contacting us on the support page at https://support.shopify.com/
You'll see links for email, chat, or telephone support on that page.
I followed the link you provided, but I don't see any email or phone support information on that page. It's been over 5 years since your post. Can you please update this info? I am in the same situation, and want to transfer a domain between my 2 shopify stores, and it's been over 5 days now waiting for results. Much thanks!