How to add the rel="nofollow" attribute for a link?

The nofollow attribute allows to point out to search robots that some links should not be followed when indexing a website.  Due to this attribute robots will not take into account the weight of the page that is referenced.

If a link is added to the text part of the block, you can go to the block Content → select the part of the text with the link → go to link editing (“insert link” option) → click on “Link color and style” → check the box “Rel nofollow”:

For a block with a button, please navigate to the block settings and check the box “Rel nofollow. Search engines don't use the link for page ranking calculations”:

If using Zero block, go to the block editor → select the element with the link → open settings panel → in the REL NOFOLLOW field select “Nofollow”: