Please ignore my post, its answered in below ticket.

https://account.infragistics.com/support-cases/5005w00001tzu1mAAA

Here you can find the modified sample.

stackblitz.com/…/igc-dockmanager-programmatically-add-pane-tabgrouppane

Thanks for the example.

stackblitz.com/…/add-new-pane-dockmanager-programatically

Can provide example for how to add new tab to the stack (Middle layer of the layout next to document 2 tab)