To create a child to an existing condition, from the Advanced Condition dialog box, click the Add button located in the same if statement of the intended parent condition:
An if statement, or child condition, is created below the parent condition. Think of each child condition as having the word "and" before it.
For example, a parent condition has one child condition. If the parent condition is true, and if its child condition is true, then the Advanced Condition is true. If the parent condition is true, and if its child condition is false, the next sibling condition is evaluated. If there are no remaining sibling conditions, the Advanced Condition is false.
For information on configuring a newly created if or else if statement, see Configuring an If Statement.