Internal links you can’t by default, I reckon.
You can try using ```<A href…> tag like this:
<a href="https://meta.discourse.org/t/use-google-search-by-default/249951" target="_blank">link text here</a>
I don’t know if it works but it is easy ti try out 
edit: did not work here
External ones follow admin-setting default other external links in new tab.