The screen is in the demonstration video of Ignition
What should I do to make the menu go down like this way?
The screen is in the demonstration video of Ignition
What should I do to make the menu go down like this way?
You're actually looking at some trickery; that's an Accordion - not a Menu Tree.
Each Accordion item body is actually a Flex Repeater, which passes information into multiple instances of a View which acts as a template. That View accepts parameters to drive things like label text and target destination (url or mounted page path).
So each of those entries ("Chart Range Selector", "Pie", "Simple Gauge") is just a View represented multiple times with different properties that have been passed into it, allowing each instance to behave in its own way.