You need VLF EPC141006 (or later) to use this feature.
This property controls how many instances of the instance level command tab containers may be concurrently open.
As a usage example, imagine a business object named Orders with a Details instance level command.
Setting this option to 3 indicates that the Details of up to three orders could be concurrently displayed.
The default and minimum value is 1, the maximum value is 9.
Using any value other than 1 means additional design and resource usage considerations apply to your application.
This option is only valid for large screen devices.
Use of this option with business object subtypes is not supported.
This property is in the Command Display tab.