It seems this question is still showing up in Google searches, 
so let me answer it. That button comes with "CloudLinux" a 
different flavour of cPanel. Vanila cPanel only has 
Nodejs 10.x that you can enable from EasyApache4. 
they do not have any eta on update for this as of this writing, 
and node 10 has crossed EOL a few months ago already. So there you go. 
No easy way to get node done if you do not have CloudLinux