Sublime 3 - multiple snippets in one file or Completions?

Question

css

Task: in css-files to do autocorrect by Tab:

1. "**" to be replaced by "==$1==" and
   
2. "****" replace with "====$1===="
   

---
As I understand it, it is impossible to write all the rules in one snippet file? (spreading snippets into files is not an option, because there are a lot of them).
Then, you need to use Completions, but this one doesn't work:

{
        "scope": "source.css",

        "completions":
        [
                { "trigger": "**", "contents": "==$1==" },
                { "trigger": "****", "contents": "==$1==" }
        ]
}

Guys, any idea why Completions is not working? Or maybe some other way to insert multiple snippets into one file?