You can configure three hotkeys for the 'Full Control' / 'View Only' connection modes using Radmin Viewer options:
Sends the <Ctrl>+<Alt>+<Del> key combination to the remote computer.
Switches the connection window view modes to 'normal', 'full screen' or 'Stretch'. More info...
Displays the window menu if 'full screen mode' is selected.
You can access toolbar function from the keyboard using 'window menu' hotkeys.