My MediaWiki test instance normally runs without Xdebug, since that gives good performance. But when I request a debug session in PHPStorm, Xdebug is automatically enabled.
I don’t often share config snippets since they are so specific to the way I have things set up. You will most likely have to adapt this to your situation. But at least it should help you to know that conditionally enabling Xdebug is possible.
I use PHP-FPM which, unlike Apache mod-php, allows you to run multiple versions of PHP. I use Apache to detect Xdebug’s cookie or query string. Then I have a separate instance of PHP-FPM just for Xdebug, with a separate php.ini.