There are two list boxes: checkbox list on the left and contents box on the right.
The left box is a check list consisting of languages supported by WinVNKey. Each language is actually the base name of a Unicode plain text file located in <INSTALLDIR>\Macros\Language. For example, Canadian comes from Canadian.txt, French from French.txt, etc.
By default, each time you check a language, all macros defined for that language alone will be displayed in the list box to the right. If any character is not available in the character set currently in effect, the entire row will be displayed in red to signify that you cannot get them by any means. All other macros displayed in black are available immediately for use.
By design, any change you make to this panel will become effective immediately and will be saved to disk so that the same setting will be used for subsequent WinVNKey runs.
List all selected files
This checkbox tells WinVNKey to display macros from all the languages selected in the left box.
Edit Files Button
If you already selected a file, clicking this button will display a dialog that allows you to edit the macros in this file. If you have not selected any file, the dialog displays an empty box with no filename.
Help Button 
Click this button to see help or explanation for language macros
Display Toggle Button 
The two list boxes can be displayed side by side or on top of each other. Click this button to change the display to best fit your viewing need.
Default button
Click this button to reset the Language control panel to the default state, which disables all languages.
Notes
By default, Vietnamese typing is always supported. It can only be turned off 99% by choosing an appropriate keyboard mode such as Literal or Sleep on the Main control panel. Or you can define a new typing method called "No Vietnamese typing," in which all edit boxes are cleared and then select this typing method in the Main control panel.