There are many ways to configure the custom fields and custom field layouts for a product. They can be inherited from the product line or setup locally for the product.
It is easy to get lost and make mistakes when configuring this. A graphical view showing connections and inheritance links would make this much more transparent and easy to understand.
Showing the different objects (Theme, Master Feature, Feature, Requirement) with their custom fields will also more or less provide a data model which would be a good documentation of the setup.
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