OK so you have a requirement in MDG that is not satisfied in the standard app.
SO you need to:
a) Check with a business analyst that cost centre category is required & something they want a user to enter
b) If the answer to a) is yes & yes then you need to use the extensibility options of that app to add an input field for cost centre category
c) if the answer to a) is yes & no then you need to look at the extensibility options in the OData service of the app &/or MDG to find a way to default the cost ctr category
d) if the answer to a) is no & no get the business analyst to fix the MDG config
Hope that helps
Jocelyn