Yes, it is indeed an idea, but is it really effective?
For example:
I am writing some text and wanna send the message → i have setted my CHBOX to → send on ENTER. ok
But then it is no more possible to do an paragraph 
.
Or i have every time when i wanna do that to CHECK and UNCHECK the CHBOX.
It would be a solution for a comment-box → that’s possible
But it can’t be a solution for a Chat-Box.
I just wondering, WHY THE CTRL-BUTTON IS NOT IMPLEMENTED ?
This button is totaly free.
So i think there is no chance to use this button, until WIX has done some changes. Or i have to use the normal-text-box. I think in the normal text-box this feature will work, althougt i did not tested it yet.
Thanks for your suggested ideas, i appreciate it.