I think creeping myrtle is another name for periwinkle, Vinca major or minor. Assuming that we're talking about the same plant, you can transplant it, trim it, prune it, run the lawn mower over it & it'll come up again.

Pull some bits out with roots on, transplant into the sparse areas and keep them watered for a while til they settle in. Vinca can be pruned fairly hard in spring after danger of frost has gone to keep it tidy. I'm not joking about the lawn mower! :-)

In the States, Creeping Myrtle is one of the common names for Vinca minor. We use the lawn mower on V. major every spring to keep it under control, but the minor isn't that vigorous here. Likely to be more vigorous in Michigan, though.