The problem (as felt by me and also as identified by the person you replied to) is that you can't copy-paste/munge some stuff into the right spot and then just let the formatter to fix the indentation. It's not a problem that the format "at rest" has whatever certain indentation to be correct, its that while being actively editing your formatter cannot automatically set the correct indentation.
The flow that you're talking about of converting yaml to json and then putting it into yaml could work in some cases but thats very much a kludge. It will have numerous bad side effects unavoidable, including that it would discard comments in the middle since JSON doesn't allow for comments at all, theres no timestamps in JSON, there's no octal numbers, etc.