One of the less sexy but more important undertakings that launched alongside Salesforce DX in 2018 was the MetadataOne initiative. This was a backend initiative at Salesforce to try to ensure that all new and existing Salesforce features would be covered by the Metadata API. All the various methods of retrieving and deploying Salesforce components depend on the Metadata API. This means that any Salesforce components that were not supported by the Metadata API could not be “externalized” as XML and so could not be version controlled and couldn’t be part of an automated development lifecycle.
I created this spreadsheet to depict the fantastic progress in improving coverage over the last few years. This also depicts the dizzying array of new metadata types that Salesforce has launched over the last number of years.