This dialog is relevant for the configuration of a local session. It is shown if you click on the [...] button next to the Main class or executable JAR text field and choose the Search classpath option from the drop down menu.

In order to select a main class, please double-click on it or select it first and click [Ok]. The main class will then be shown in the Main class or executable JAR text field of the local session panel. You can also leave the dialog with the [Cancel] to avoid making any changes to the configuration.