You can define a TeX translation associated to any character of the user font the following way:
    first you change the font to the User font by clicking on the menu :
Fonts->Temporary Change->User
    then you open the User-Keyboard by example by clicking right  on the mouse then selecting Show actual keyboard;
    second you choose a character by clicking left on it;
    third you type the TeX translation you want in the text field which appears at the bottom of the windows. You finish by hitting the Enter key.
    Each time you put this character (of the user font) in your document, it will be replaced by its translation and the preview will reflect it.
    This allows you to use the special TeX macros you put in a format file in the same directory.
    To have an example, click here.