In my opinion if you can remember what each clause actually is, I would save each one as a building block with a short logical name eg ca1, ca2, ca3, cb1, cb2, cb3, cc1, cc2, cc3
Then to insert one in your document type the relevant name and press F3 (or Enter)
If you don't know the contents of every clause by heart then you can still use building blocks and apply gallery and categories to each one to give you a way to organise them. Then you can add buttons on your ribbon which display the optional clauses for each Gallery/Category variant. See this page for extremely detailed information relevant to this approach
Building Blocks & AutoText