Using Rel=”external nofollow” instead of target=”_blank”

Hi;

Target codes are not working anymore in current web technologies. According to this, it’s very important to open links with Rel=”external” code for SEO.
I want to target my links with Rel=”external nofollow” instead of target=”_blank”.
The Rel command is not working in my page when i try to write it manually. Also the social icon links are using target code in Enfold Settings.
Do you have any suggestions other than plug-in to solve this problem?

Thank You;
Hande