Currently, the extension, TabberNeue has a bug where the contents of nested tabs are truncated by the height of one tab header. The contents only display properly after one clicks on a top-level tab header.
Text truncation demo
The line, Live2D Modeling: Naname, does not display until you click on one of the top-level tabs.
Image truncation demo
The image is truncated at the bottom until you click on Super tab.