Can I use the templates to create a new contract of an IRS with one year duration quarterly floating cashflows on the libor and 6 month for the fixed leg?
Any arbitrary IRS can be represented within the CDM, however, the schemas are quite complex. You can find examples in the examples/NewTrade directory in the repo.
While in theory possible for these contracts to be created from a UI, the schema complexity makes this incredibly cumbersome and error-prone. CDM is a data standard meant to be produced and processes by code, not by humans. What you could do, is create a helper contract that does the heavy-lifting of creating a full CDM swap based on a few inputs you provide it.