I can understand the frustration this can cause for some of our users and while this is something we are working to add in to our current editor our engineers prioritize the requests based on customer feedback. Right now this issue has not had a lot of customer requests. Everyone in this thread has already been added to the feedback requesting this feature and I've just updated the request again.
This is critical functionality for various reasons including managing subscribed lists based on actions taken by a contact and to track affiliate/partner conversions via links. This severely limits transactional email options. The fact that this is not available currently and is apparently not a priority is baffling. It seems CC is focused on simple use cases that do not include API integrations and serious marketing. I'm frustrated that I have spent time developing to an API where maintenance and functionality is not a priority. Other developers beware!
These are additional issues:
Unable to GET a list of custom fields via the API
Unable CRUD custom fields with names via the API
Just recently the options to update custom fields via the API have stopped working
Unable to use dynamic links
When editing lists or contacts, unable to see current tags or lists in UI
Receiving this response intermittently when using the API: Service Unavailable: Back-end server is at capacity 503