>>19
以下をuserChrome.cssで出来るよ

/*動画サイト再生時にファビコンとサウンドアイコンを表示*/
.tab-icon-image:not([pinned]){opacity: 1 !important}
.tab-icon-overlay:not([pinned],[crashed])[soundplaying]{
opacity: 1 !important; border-radius: 9px !important; top: -6px !important; inset-inline-end: -12px !important;z-index: 1 !important;margin-right: 12px !important; color: inherit !important;background-color: #00000000 !important; !important; fill-opacity: 1 !important; padding: 0px !important; height: 16px !important; width: 16px !important;
}