Yesterday I have got an answer on Stack Overflow https://stackoverflow.com/questions/49982755/how-to-access-system-stores-for-shopping-world-element/. Turns out I have not configured two required properties ‚displayField‘ and ‚valueField‘ which, as I have understood from example in anwer, are specifying which model properties are used for option’s text and value. There is no description of this properties in documentation, so it was totally unclear what they do.