Allow creation and execution of change set to be performed in separate steps

As a platform engineer, I want to be able to create a change set in a separate step from executing the change set, so that I can allow approval of the changes prior to execution.

At the moment, it's possible to create a change set, but there does not appear to be a way to execute a pre-existing changeset, nor a way to retrieve the ID of the changeset which was created.