This initiate a dialog to add a parameter, Binary, Object or Function.
For convenience it will always show the last parameter you have selected as input.
Note that you can define the parameter type implicitly, using the pre-defined syntax (see also QuaestorSyntax):
You can also use the Value or String button (which are the two most important differences for Quaestor). Furthermore you see that a Binary, Object, Function() and Document button are available. These buttons are used for the following:
Note that due to some choices in design, a string parameter in Quaestor cannot be changed to a value type (so removing the $ will not help...). In that case you have to create a new parameter with the correct type.