Hi Avi,
Since the Sequence Editor does not have an API, you will not be able to highlight steps. However, you can search through the sequence for steps that are of a certain step type and display these in a list. You can obtain a reference to the Step Type object and use the property StepType.Name to get the name of the step type.
National Instruments recognizes the importance of a search and replace tool and will be considering such a tool in future versions of TestStand. I hope this helps.