How can I change the icon size of the right vertical toolbar?

Version 6.1.0.3.

In the Settings → LibreOffice → View, I see Toolbar/Sidebar/Notebookbar icon sizes. It seems that Toolbar means the main toolbar, and Sidebar means the panels that can be shown by clicking the icons on the right vertical toolbar. But how can I change the icon size of the right vertical toolbar?

It seems that you can’t.
If you think that important enough you can file a enhancement request: https://bugs.documentfoundation.org