hi, that sounds like a feature-request: I would log it: https://github.com/elastic/kibana/issues/new/choose
As for digging in the source-code, this is probably a good entry-point: https://github.com/elastic/kibana/blob/15c0644c9756eb58e86cef7e7cd1ce8266bc7ed0/src/plugins/discover/public/application/angular/context/api/context.ts#L60