How to update Azure Marketplace to support complex custom attributes in SCIM provisioning

We have a gallery app listed on Azure Marketplace, which supports SCIM provisioning and would like to update it to support provisioning of a custom SCIM extension with a complex attribute like so:

{
	"schemas":[ "urn:ietf:params:scim:schemas:core:2.0:User"],
	"urn:ietf:params:scim:schemas:extension:customExtension:2.0:User": {
    	"customAttributes": {
        	"job_code": "PM123456"
			"job_family": "Support"
    	}
	}
}

This documentation suggests that "Custom multi-value and complex-typed extension attributes are currently supported only for applications in the gallery." It also seems that update requests to Microsoft Entra app gallery are now handled on a case by case basis according to this page.
This seems to work with update requests (PUT/PATCH) when using dot-notation, however does not work for create requests (POST). Does anyone know how this should be structured in Entra provisioning schema so it works for both update and create requests?

For context - we've tried adding a custom attribute mapping using dot notation (urn:ietf:params:scim:schemas:extension:customExtension:2.0:User:customAttributes.job_code) which returned the following:

{
	"schemas"
	"urn:ietf:params:scim:schemas:extension:customExtension:2.0:User"
	{
		"customAttributes":"PM123456"
	}
}

as well as using colon sub-attribute (urn:ietf:params:scim:schemas:extension:customExtension:2.0:User:customAttributes:job_code) to define the mapping - this was closer, but still not the expected structure:

{
	"schemas": [ "urn:ietf:params:scim:schemas:core:2.0:User"],
	"urn:ietf:params:scim:schemas:extension:customExtension:2.0:User:customAttributes":
	{
    	"job_code": "PM123456"
	}
}