Add Custom Button To MenuOverLay

WebViewer Version: 8.4.1

is there a way to add a custom button here:
Screen Shot 2022-05-23 at 1.55.18 PM

I’d think something like the following but it doesn’t seem to work for specifically those menu items:

header.get('fullscreenButton').insertAfter(
    {
      type: 'actionButton',
      title: 'Custom Button',
    }
)

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never mind this. PDFTron WebViewer Interface: MenuOverlay was exactly what i was looking for