Zen Browserで「新しいタブ」ボタンを固定するCSS

#navigator-toolbox[zen-expanded="true"],
#navigator-toolbox:is(#navigator-toolbox[zen-user-hover="true"][zen-has-hover], #navigator-toolbox[zen-user-hover="true"]:focus-within, #navigator-toolbox[zen-user-hover="true"][movingtab], #navigator-toolbox[zen-user-hover="true"][flash-popup], #navigator-toolbox[zen-user-hover="true"][has-popup-menu], #navigator-toolbox[zen-user-hover="true"]:has([open="true"]:not(tab):not(.zen-compact-mode-ignore)), #navigator-toolbox[zen-expanded="true"]:not([zen-user-hover="true"])) {
 
    #tabs-newtab-button {
        position: fixed;
        bottom: 50px;
        z-index: 100;
        width: 14% !important;
    }
 
    #tabs-newtab-button::before {
        content: '';
        display: block;
        height: 1px;
        background: light-dark(rgba(1, 1, 1, 0.075), rgba(255, 255, 255, 0.1));
        width: 100%;
        position: absolute;
        top: -8px;
        left: 50%;
        transform: translateX(-50%);
    }
 
    #tabbrowser-arrowscrollbox {
        padding-bottom: 30px;
    }
 
    hbox#tabbrowser-arrowscrollbox-periphery::before {
        display: none !important;
    }
 
    #tabbrowser-arrowscrollbox[orient="vertical"] {
        &[overflowing]:not([scrolledtoend]) {
            mask-image: none !important;
        }
    }
}
 
 
#navigator-toolbox:not(#navigator-toolbox:is(#navigator-toolbox[zen-user-hover="true"][zen-has-hover], #navigator-toolbox[zen-user-hover="true"]:focus-within, #navigator-toolbox[zen-user-hover="true"][movingtab], #navigator-toolbox[zen-user-hover="true"][flash-popup], #navigator-toolbox[zen-user-hover="true"][has-popup-menu], #navigator-toolbox[zen-user-hover="true"]:has([open="true"]:not(tab):not(.zen-compact-mode-ignore)), #navigator-toolbox[zen-expanded="true"]:not([zen-user-hover="true"]))) {
 
    #tabs-newtab-button {
        position: fixed;
        bottom: 150px;
        z-index: 100;
        margin-left: 5px !important;
    }
 
    #tabs-newtab-button::before {
        content: '';
        display: block;
        height: 1px;
        background: light-dark(rgba(1, 1, 1, 0.075), rgba(255, 255, 255, 0.1));
        width: 100%;
        position: absolute;
        top: -8px;
        transform: translateX(-50%);
    }
 
    #tabbrowser-arrowscrollbox {
        padding-bottom: 40px;
    }
 
    hbox#tabbrowser-arrowscrollbox-periphery::before {
        display: none !important;
    }
 
    #tabbrowser-arrowscrollbox[orient="vertical"] {
        &[overflowing]:not([scrolledtoend]) {
            mask-image: none !important;
        }
    }
}