Render to File dialog has many options.
Sounds like you want the "Stems", or "Selected tracks via master" option. The first one doesn't apply master FX, the latter one does.
Or are you talking about in-project render? In that case create a new track, then select your wanted tracks to mixdown, send them to the new track you created, then render the output of the receive track, and mute the source tracks. You could also create a custom action for this, so that it's much faster if you use this sort of functionality often.