Hi Tarek,
The text object is defined in a Text.xfo file, on my system it is under C:\Users\BR001\AppData\Roaming\Adobe\Designer\10.0\EN\Objects\Standard.
You can find out the location by looking at the Group Properties of the Standard Object library;

You can also create your own widget, set it up on the design view how you want and then do right click "add to library" (option has moved, but that's what ES3 has). But I don't think you can get your own ones to show up in the dropdown when trying to convert objects.
Bruce