N/ui/serverWidget Module
Form.insertTab()
Method Description: Inserts a tab in front of another tab.
Returns: void
Supported Script Types: SuiteScript 2.0 Suitelet Script Type and SuiteScript 2.0 User Event Script Type (beforeLoad(scriptContext))
Governance: None
Module: N/ui/serverWidget Module
Since: 2015.2
Search NetSuite - https://system.netsuite.com/app/help/helpcenter.nl?search=Form.insertTab(options)

// Code Example 1

//Add additional code

//...

var form = serverWidget.createForm({

    title : 'Simple Form'

});

var tab1 = form.addTab({

    id : 'tabid1',

    label : 'Tab'

});

var tab2 = form.addTab({

    id : 'tabid2',

    label : 'Tab'

});

form.insertTab({

    tab: tab2,

    nexttab:'tabid1'

});

//...

//Add additional code



//SOURCE: https://system.netsuite.com/app/help/helpcenter.nl?fid=section_4340351224.html