When Rekall executes an event function, it will always execute whatever is in the event function, be it a script or a macro. Similarly, if you edit an event that contains a script or a macro, then Rekall will act appropriately. However, if you edit an empty event, Rekall needs to know whether to use a script or a macro. By default (for compatability with earlier releases), scripting will be used. To change this, go to the View menu and bring up the Options dialog; under the Script/Macro tab there is a setting which controls rekall's behaviour. There are three options; to always use scripts (the default); to always use macros; or to prompt whenever editing an empty event.
Note that this setting is not relevant if you create macro modules. These are accessed via the Macro tab in the main database window.