The Expressions Panel
The Expressions Panel is a dictionary of all the expressions available in your project. It is shown floating next to the Parameters dialog. By default it is semitransparent so it does not distract you while entering parameters. The Expressions Panel can be hidden or shown by pressing F4.
The search box in the top right can be used to quickly filter the object list.
Double click an object to list all its expressions. Descriptions are also shown next to each expression to help indicate what value will be retrieved. Double click one of the listed expressions to insert it to the current expression in the Parameters dialog. Press Escape or click the Back button to return to the object list.
Behavior expressions are also shown for objects with behaviors. The System page also lists all system expressions, global variables and local variables which are in scope (see Event Variables).