GitHub announces the ability to customize code scanning default setup at scale using a new repository property `github-codeql-config-file`, a new syntax for referencing configuration files in other repositories, and support for private registries to access private config files. This is now generally available on github.com and will ship with GitHub Enterprise Server 3.23.
From the source
You can now apply your own configuration file to code scanning default setup, using the new github-codeql-config-file repository property.
github.blog