Nested menus are only possible with single-select menu question types. These types of menu questions allow you to present multiple menus for a single question in your design. In this way they are used to refine a question and ask more details depending on the answers selected.
The important thing to notice with nested menus is that only a single answer is collected as a combined response. If you want data to be collected on each menu response you would use multiple menu questions rather than a menu with multiple nested menus.
It is possible to attach validation to menu questions. This is done using the Validations button. Click on this button to show a screen similar to that the one below, showing the nested menus and the valid combinations.
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