You can use Transaction action on the left pane of the ScenarioBuilder to divide your Scenario into meaningful sections. Each Transaction is a section of the scenario (consisting of a sequence of actions) marked for the purpose of measuring the performance (response time) of that section within the scenario. Transactions let you know the exact point where the failure or slowness occurs when playing back the scenario against your target application.
For example, you can define a Transaction to be "login to CRM" where the beginning of the Transaction is defined when the CRM application is launched, and the end of the Transaction is defined when the CRM interface finishes loading on the screen. Many Actions may occur within a Transaction (such as finding the executable to launch the application, launching the executable, waiting for the login screen, typing in the login name and password, waiting for the application to load completely, etc.).