Registering backup repository via configuration file

Is this possible to register a repository for snapshots via configuration file instead of API ?

it is not clear from previous discussions Register snapshot repositories via config file?

No, it's not possible.

Does it make sense to add ANY AWS Cloud specific configuration to elasticsearch,yml if I plan to use the plug-in only to enable "repository for snapshots" feature? In other words, in the plugin's wiki all the parameters like region, bucket, access and secret key are passed to the API as parameters. Does this mean that their equivalent values (if specified) from elasticsearch.yml (e.g. or are simply ignored?

Yes, the parameters specified using API take precedence over parameters specified in config file.