YAML to JSON is probably doable, JSON back to YAML not so much.

There are multiple ways to mark multiline strings in YAML. Then there are anchors, like bionicjoey mentioned. Also comments, YAML has them. You'd have to have some way to retain the extra information, if you want to make the full round trip.

Here's an example:

def-db: &def-db
    # here be dragons
    login: admin
    passwd: nimda
    
prod:
    db: *def-db
    desc: |
        I'm a teapot
        short and stout

dev:
    db: 
        <<: *def-db
        passwd: pass
    desc: "I'm a teapot\nshort and stout\n"

converted to JSON looks like this

{
    "def-db": {
        "login": "admin",
        "passwd": "nimda"
    },
    "prod": {
        "db": {
            "login": "admin",
            "passwd": "nimda"
        },
        "desc": "I'm a teapot\nshort and stout\n"
    },
    "dev": {
        "db": {
            "login": "admin",
            "passwd": "pass"
        },
        "desc": "I'm a teapot\nshort and stout\n"
    }
}