PdfTron with multiple documents: Hide header items (multitab)

WebViewer 10.x / PdfTron

WebViewer can display multiple (PDF) documents since 8.x. Like so:

WebViewer({
    //disabledElements: ["toolsHeader", "header"],
    initialDoc: ["first.pdf", "second.pdf"]
  }, viewerDiv)...

What we see is:
enter image description here

I would like to keep the multi tabs to switch between documents (marked green in the screenshot), but I want to remove the header items below (marked red).
I tried my best to disable features or elements using instance.UI.disableFeatures(...) and instance.UI.disableElements(...), but I didn’t succeed without breaking the UI or removing both multitabs and header items.
https://docs.apryse.com/api/web/UI.html#.FeatureFlags__anchor

How do I keep the multitabs (TabsHeader) open, but remove the header items below completely? Can it be done using disableFeatures|Elements or is there another way?

Thanks