Creating Complex Expressions 
You can add complex expressions in the following rule entities:
Action values in a decision table
LHS of a condition and assign action types in an If-Then rule
Definitions
In the Rules Navigator view, expand the project node and select the ruleset or flow ruleset.
The ruleset or flow ruleset overview page opens in the Editor Window.
Adding Compound Expressions in Action Values in a Decision Table
Open the decision table in the Editor Window.
In the context menu of a cell under the action column, choose Advanced Edit.
The advanced editor opens.
Choose the value and in the drop down menu, choose Add a New Expression.
Adding Compound Expressions in Condition and Action Types in an If-Then rule
Open the rule in the Editor Window.
Under the Conditions or Actions section, choose the RHS value and in the drop down menu, choose Add a New Expression.
Adding Compound Expressions in a Definition
In the Project Explorer view, select the definition.
The definition opens in the Editor Window.
Under the Fixed Definition or Variable Definition section, choose the RHS value and in the drop down menu, choose Add a New Expression.
Choose the operator and in the drop down menu, select the relevant operator.
Add dynamic or static value to the compound expression.
Adding a Dynamic Value
Choose the value and in the drop down menu, choose Set Dynamic Value.
In the dialog box that appears, choose the dynamic value.
Choose Apply.
Adding a Static Value
Choose the value and in the drop down menu, choose Set Static Value.
An inline text box opens.
Enter the value in the inline text box.
You can also add brackets in the compound expression.
Adding an Open Bracket
Choose the value and in the drop down menu, choose Add Open Bracket.
Adding a Close Bracket
Choose the value and in the drop down menu, choose Add Close Bracket.
Deleting a Complex Expression
Choose the expression and in the drop down menu, choose Delete.