You can define a TeX translation associated to any character of the user font the following way:
first you open the User-Keyboard by example by clicking right on the mouse then selecting Show the user Font keyboard;
second you choose a character by clicking left on it;
third you type the TeX translation which appears in the text field 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.