Unlike other format types, you can reference subformats even if they are not defined in the same format-file chain as the referencing format. For example, if you reference LightBorder in a table format, but LightBorder is defined only in your page-layout file, DITA2Go can find the definition. However, any definition in the file that contains the reference overrides definitions of the same subformat in other format configuration files.
You define subformats in a format configuration file referenced either from another format template file or from your project configuration file; see §7.2 Working with format configuration files.
To reference a subformat configuration file:
[Templates] ; Subformats = path to a file where format components are defined Subformats=%omsyshome%\d2g\formats\d2g_subformats.ini
Subformats specifies a path to a general subformat file, for use when a subformat is missing in the present format or general configuration file. If a subformat is defined in both the referenced and the referencing file, DITA2Go uses the definition in the referencing file; the definitions are not merged.
Associated with certain subformats are labels, headings, and other fixed text components. The default settings for these text values are located in language configuration files; see §8.10 Localizing output headings, labels, and names. You can override the default values in your project configuration file, or anywhere in the chain of general configuration templates; but not in a subformat or format configuration file.