When the Options menu is hidden (Hide Menu = Yes) you have to specify a Menu Toggle Key in the Emulation Parameters in order to toggle the Options Menu on and off. In the example below I am using the Alt-O key combination in order to toggle the Options Menu. Note that I also have the Hide Menu option set to Yes.
To my knowledge you can't configure this manually on the device, but rather in the desktop configurator from a PC or an Avalanche Server. The Emulation Parameters in the desktop configurator provide access to countless more settings than what are available within the basic options within the settings on the device.
If you are referring to the Taskbar (bottom of the screen on a Windows CE device) and not the Options Menu (top of the screen) then that is dictated by your AppCenter configuration and not TelnetCE.
I set the Hide Menu to No and added the toggle, in case it happens again.
I now see the menu again.