I don't know what do you mean with "I have not received any answer from FSDT for weeks", since you made two posts on this forum, one I already replied to, and this one, and I don't have any emails from you.
Maybe you tried to contacted us on Facebook, because you have ignored the advice on the Facebook page which says not use it for support ?
In any case, to reply to your question, you are not supposed to have any Couatl.INI file on your system by default, unless you create one yourself OR you enable logging in the Troubleshooting section of the GSX Settings, which will create one with that just option.
So, if you need to add something to it, and it's not there, just create it from scratch.
The easiest way is probably to enable logging in the Troubleshooting section of the GSX Settings first, so it will be created for you, which might be easier and less prone to errors than having to create one from scratch.