Hello, @dev13 and welcome to the Liquibase community!
I’ve been able to gather some info from our internal team to help you with this issue, but first, I wanted to mention that we are currently at Liquibase version 4.9.1, and this post is from 4.5. if you’ve updated your version to 4.9.1, are you still having this issue?
There are a couple resources you may find helpful in formatting your schema validation using JSON/MongoDB/Liquibase. You’ll need to wrap your JSON validation code in order for Liquibase to process it, as we currently only support XML in MongoDB.