There does not appear to be any support for running a wizard update for a REST connector defined with JSON at least as of 7.2. Is there support for it in a higher version? Is this on the roadmap as an enhancement?
Even though there were multiple enhancements to the rest Integration wizard in Pega 7.2.1 and it has been improved which allows you to connect to complex rest services, there is still no update wizard for REST integration. You still have to do it manually.
There is still no plans for that as far as I know.