When you make use of the Website URL action it's possible to add a rel attribute with several values, like nofollow, noreffer and noopener. You can find a list of options below.
nofollow
You can use nofollow to link to documents or pages where you do not want that Google follows a link, for example a paid link.
noreferrer
Usually you can see the URL from what page or site the user came from when entering your website. When you use noreferrer it will not send the current URL to the new page when clicking on the button.
noopener
With JavaScript you can read the property window.opener which gives you access to the document from the prevous page (the opener). If you're linking to an external website, you might want to use noopener to make sure the site cannot access your page or document, this improves your sites security and unwanted changes of your document.
external
Indicates that the linked page is not part of the same site and links to an external site.
alternate
Links to a document that is an alternate representation of the current page. For example, a PDF, translated page or mirror.
next
A link to a document or page next in the series .
prev
A link to a document or page previous in the series.
help
Provides a link to a help document or page.
