Is it possible to move domains between subscriptions or merge subscriptions?
When a full subscription is moved, mail and DNS settings for domains will be moved to another owner as well.
There is no ability to move domains between subscriptions or merge subscriptions, but there is feature request. Vote for it to increase the importance of the feature.
As a workaround, remove a domain in subscription and then create it for another subscription:
Note: Mail accounts will not be moved.
Create a new subscription example2.com in Subscriptions > Add Subscription.
Copy your original website into example2.com subscription via Domains > example.com > Website Copying.
Test the website on its new location by adding domain.tld into hosts file on local computer.
Remove the original website via Domains > example.com > Remove Website.
Rename example2.com into example.com in Domains > example2.com > Hosting Settings.