Thanks all of you that have helped me understand the situation.
 
On the OP I inserted:
 
What is suggested in the title will not work. To quote scook:
“Plug-in output is not recorded in SONAR. The only solutions are VST recorders, loopback (with physical and virtual audio connections) and bounce using live input. That is it, there is no more.”
 
If there is more I should do please let me know.

Let me re-phrase the above post and perhaps get some feedback:
Is there anything to be gained by opening the programs separately, not as VST/host nor rewire. This way both programs have the hotkey focus when their window is on top. Correct?
 
Will I be able to copy/paste or drag/drop audio tracks or clips between these two DAW's? How about to copy/paste or drag/drop midi notes or midi track or clips? My FL Studio 11 has stopped working.

Have you tried running the vsti stand alone and use vitual audio cable?

http://vb-audio.pagesperso-orange.fr/Cable/

js516
Have you tried running the vsti stand alone and use vitual audio cable?

http://vb-audio.pagesperso-orange.fr/Cable/

Thanks. I will add this to my list of work-arounds.

 
For what it's worth, senderella can still be had here :

 
http://web.archive.org/web/20070226050709/http://subminimal.org/tools.php
 

 
I haven't used it so can't comment on it.  Though it may not solve the current recording problem, it may be useful for other things as mentioned in the SOS article.