Google reported that the beta version of the Schema.org markup validator is already available to testing.
Microlayer validator – a tool whose main purpose is to check the syntax and compliance of markup with Schema.org standards. It will also alert users if they use Schema.org types and properties in unusual combinations. This will help avoid problems with displaying information in the rich snippet.
This tool was “based on the tool formerly known as the Google Structured Data Testing Tool (SDTT)” and is similar to Google’s version:

However, the Schema.org validator has an advantage. Google’s tool only displays the structured data schema that Google supports. And the Schema.org micro-markup validator supports more types of structured data, including those that Google doesn’t use.
As a reminder, last July Google announced that will refuse support structured data validation tool, and in December the company announced that will transfer this tool from Google to Schema.org by April 2021.
A source: Seroundtable