Configuring Filebeat to use an AWS PrivateLink endpoint to index into CloudWatch

Continuing the discussion from AWS PrivateLinkの使用方法:

I also want to do this. I can't find any documentation to configure an endpoint override.
I also need to do the same thing with the S3 snapshots repository.

Is it even possible right now?

According to the docs on s3-repository I need to set the endpoint and region properties in the keystore, for example:

bin/elasticsearch-keystore add s3.client.default.endpoint
bin/elasticsearch-keystore add s3.client.default.region

It's still unclear how to do this for filebeat CloudWatch integration.