Nope, that is outside of what CSS is designed to do. CSS is primarily for styling HTML elements.
The only way I can think of to insert links without touching the source code would be to use Javascript or jQuery. But that would require a fairly sophisticated programing solution and isn’t worth the trouble.
But if you did want to edit the source code, it isn’t really a big deal. The only caveat is that you’ll want to back up the edited file(s) when upgrading and apply your edits to the new installation. Super easy!