I would recommend continuing to use the Remote Support desktop software primarily for now. As soon as we add the ability to send a ctrl-alt-delete in RescueAssit, we will update this post.
I just got a subscription to RescueAssist today because GoToAssist was no longer available (which I have used previously). How could this not be incorporated into your initial release of this product!? I would imagine that a majority of users need the ability to do this.... especially with unattended support.
I would like to thank everyone for their patience as we worked to get the ctrl alt del functionality back into the product. I am happy to report that this functionality was released earlier today and you can now access ctrl alt del from the menu bar while a session is running in admin mode: