Yes, it's the Input Control menu command that can now be used to add text boxes or comboboxes to the menu.
The way it works is that when the user enters or selects something in the text box or dropdown the system first sets the value of some attribute in the LoggedInSystemUser (recommended) or SystemSettings object to the value entered or select by the user. Then it executes some command that you define that can use this value to do whatever it wants. For example, in the Library a query is run that uses the entered value and displays the search results:
FIND Item WHERE Item.Title CONTAINS LoggedInRegularUser.TitleFilter
So when you define this control in the menu in the Config. Tool you first need to define an attribute that will be used by the subsequent command and then define the command itself - see how this is done in CRM and Library.
Trigger button if defined is the button that is displayed next to the textbox or a drop down. Pressing this button triggers the command (same as pressing the Enter key).
Checkboxes whether to display choices are only enabled if the attribute that you map this control to has choices. In this case these choices may be displayed in a drop down instead of the textbox (provided that you tick the appropriate checkbox)
