The edit campaign endpoint in the REST API is very limited: it only allows changing name, alias, description and isPublished. There’s no way to edit the actual campaign flowchart through the API.
Our use case is that we have a campaign that is re-used every few months to send 30+ emails, each scheduled on a particular date. To update the dates manually is tedious and error-prone. (The “after a relative time period” option doesn’t work for us, because late subscribers are not supposed to lag behind; they should receive each email at the same moment as everyone else.)
I appreciate that such an API will be more difficult to implement than simple scalar field editing, but it would be very useful for us.