Multi-delete can be used in Core Data Lab after enabling setting Allow multiple selection in the Tables section of the Core Data Lab Preferences..
Database extensions can be added and removed in the Supported database file extensions edit box, located in the Search section of the Core Data Lab Preferences.
In order to open a Core Data database in editable modus, you need to add a compatible Core Data object model to the Core Data Lab project. This may be a cached object model, an object model embedded in an app or an object model file. More info about how to setup a project can be found in the Core Data Model Help.
Follow these steps to remove the readonly status of a project that has a compatible Core Data object model: