Last year in May I asked this question:
Is there a possibility to change the CSS of the tab-title of a tab that is active? It is the discussion #3482.
Today I recognized that if the sidebar is visible, then two tabs have the same CSS, because two tabs are active. So, I'm looking for a selector name where I can define the CSS for the tab that is in focus. It is not `notebook tab:focus label`.
Thank you very much for an answer in advance.