yes i know, i writed about this (that i know this method), but i suggested advanced mode…
I remember posting about this but the renoise team seemed to not really like the idea.
I guess it has to do with the word “render”. You cannot really render a synth… ok, then call the feature “Record and render”, “Export in realtime”, "Export mixdown, whatever.
It is really difficult from a user point of view to understand, when you have a track that outputs an audio stream, why it can’t just be saved to disk when exporting in realtime. The same applies for the function “Render selection”.
It is even more difficult to understand since Renoise can record audio with no problems.
+1 for this one.
At this time my workaround is to use Silverspike Tape It. You can synchronise multiple instances of it and have it record in sync with Renoise… but it would be so nice to have it directly in Renoise
It’s nothing wrong with the idea. Who said that?
It’s just a current technical limitation that makes this impossible to do right now.
Renoise disable your soundcard when rendering.
So there are quite some changes that has to be done to be able to render real realtime.
However, this idea is so good that I would be surprised if we will not see it some time in the future 
+1
Actually I always use Reaper to save the external audio tracks and mix to the renoise audio to create the final render.
i use pattern record in renoise, but it would be great to have real time render function for that…