Should chocolate plants be trimmed back in the fall?
Yes if the plants are perennials, no if they are annuals, BUT annuals plants give you seeds for the next years IF you like to try grow from seeds, Perennials can give you seeds, cuttings or split the plants by lifting out the ground and taking small parts of the parent plant that has small roots attached, pot these up and replant the parent plants, when foliage dies down, remove, add a layer of humus around the root area and next year they will flower again, give a feed as for slow release such as fish / bonemeal and blood. rake this into the soil as you tidy for winter.
Best of luck and kindest Regards.
If you are asking about Pseuderanthemum alatum, It is a tender perennial that would be treated as an annual in your area. It will reseed quite likely, but it will not survive the winter outdoors.
Or, is this your plant?
Hardy to zone 7, otherwise dig the tuber and store it in a non-freezing location over the winter. Perhaps in a pot.