The Cards you are going to create, the Pages you are going to display on the panel are configured in scripts without any information about the NSPanel Items they should run on. This information is provided by the calling CallBack rule, which is triggered by the panel you are working with. This way you can re-use the same Card for different Panels in your automation.
To get the information about this Context Target you can use this statement. Now you are able to build for instance links to other pages on your own by sending the loadPage-request to the context NSPanel Item.
Openhab Blockly Nspanel - Library Documentation