When adding a region segment, the segment editor is currently suggesting the internal region code
Those are not really helpful.
It would be a big improvement if the available regions would be suggested instead.
As the internal region codes are ambiguous we would need to map the selection to a segment filtering by region and country.
So selecting "Bayern" as region would segment by (country=DE and region=02)
Just FYI: That be also useful for #4633 maybe. There I am doing this "manually": eg https://github.com/piwik/piwik/blob/2.11.2/plugins/UserCountry/API.php#L72-L73 and https://github.com/piwik/piwik/blob/2.11.2/plugins/UserCountry/API.php#L117-L118 . If we have a mapping for this we could use this as well there. Same for deviceDetection etc https://github.com/piwik/piwik/blob/2.11.2/plugins/DevicesDetection/API.php#L200-L201