1) Create new form
2) Open form builder
3) Drag&drop 'select' control from left panel to the form
4) Open 'API' tab
5) In field 'Custom Properties' click 'Add another'
6) Write key = 'attribute' and value = 'contracts:contractWith'
7) Save control and save form
8) Open edit/create form with our select control
Expected: in the select control will be options 'Исполнителем' and 'Заказчиком'