I apologize for the misleading previous reply, I didn't realize that the question was about Mac/Linux Viewer.
Unfortunately, there is no such feature in Beta 1 yet, as it has limited functionality. However, the Send Ctrl+Alt+Delete feature will be implemented at subsequent stages (such as beta 2, beta 3 etc.) or the final release.
This is to inform you that we released the updated Beta of the Viewer for Mac where we implemented the Send Ctrl+Alt+Del feature along with the advanced mouse scroll and displaying remote cursor shape. A full list of features that are already implemented or will be implemented in future updates is available here.