Fx 133 > Tableiste unten per CSS-Code, oder per Skript.

/* -------------------------------------------------*/
/************* aktiven Tab einfärben ****************/
/* -------------------------------------------------*/

.tab-background[selected="true"]{
    background-color:transparent !important;
    box-shadow: inset 0px 0px 40px 0px #2846fa !important;
}


/* -------------------------------------------------*/
/************* Tab ICON LAUTSÄRKE Größe ****************/
/* -------------------------------------------------*/


.tab-icon-overlay {
  fill: white !important;
  transform: scale(1.5, 1.5) !important;
}

/* -------------------------------------------------*/
/************* Mehrzeilige Lesezeichen-Symbolleiste ****************/
/* -------------------------------------------------*/


/*Mehrzeilige Lesezeichen-Symbolleiste*/

@-moz-document url-prefix("chrome://browser/content/browser.xhtml") {
     #PersonalToolbar {
        max-height: calc(25px * 3) !important;
    }
    
    #personal-bookmarks,
    #PlacesToolbar,
    #PlacesToolbar > hbox {
        display: block !important;
    }
    
    #PersonalToolbar toolbarbutton {
        min-height: 25px !important;
        max-height: 25px !important;
    }
    
    #PlacesToolbarItems {
        max-height:60px!important;
        display: flex!important;
        flex-wrap: wrap!important;
        overflow-x: visible!important;
        overflow-y: auto!important;
    }
    
    #PlacesToolbar,
    #PersonalToolbar > scrollbar {
        -moz-window-dragging: no-drag !important;
    }
    
    #PlacesToolbar #PlacesChevron {
        display: none !important;
    }

}


/* -------------------------------------------------*/
/************* Lesezeichen Sidebar - Ordner Icon gelb ****************/
/* -------------------------------------------------*/

/* Lesezeichen Sidebar - Ordner Icon gelb */

@-moz-document url("chrome://browser/content/places/bookmarksSidebar.xhtml") {
treechildren::-moz-tree-image(container) {
list-style-image: url("data:image/gif;base64,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") !important;}
}



/* -------------------------------------------------*/
/************* Lesezeichensymbolleiste - Hintergrundfarbe ****************/
/* -------------------------------------------------*/


/* Lesezeichensymbolleiste - Hintergrundfarbe */
    @-moz-document url("chrome://browser/content/bookmarks/bookmarksPanel.xhtml"), 
    url("chrome://browser/content/browser.xhtml"),
    url("chrome://browser/content/history/history-panel.xhtml"),
    url("chrome://browser/content/places/bookmarksSidebar.xhtml") {
    #bookmarks-view,sidebarheader,#sidebar-box,.sidebar-placesTreechildren,#sidebar-search-label,#sidebar-search-container,#placesList > treechildren{
    background:#000000!important;
    color:white!important;
    }
    }


/* Tableiste unten*/
#TabsToolbar {
    position: absolute;
    display: block;
    bottom: 0;
    width: 100vw;
}

#navigator-toolbox {
    position: relative;
    padding-bottom: calc( var(--tab-min-height) + 8px );
}

.titlebar-buttonbox-container {
    position: fixed;
    right: 0;
    visibility: visible;
    display: block;
}

#TabsToolbar .titlebar-buttonbox-container,
#TabsToolbar #window-controls {
    display: none;
}

#main-menubar {
    height: 28px !important;
}
          

/*...................Ab hier nur Privater Modus...................*/

/* Das lila Icon für privaten Modus oben rechts eingefügt */
#main-window[privatebrowsingmode=temporary] #PanelUI-button::before {
    margin-left: 0 !important;
    margin-right: 0 !important;
    content: '' !important;
    display: block !important;
    width: 20px !important;
    height: 30px !important;
    background: url("chrome://global/skin/icons/indicator-private-browsing.svg") !important;
    background-repeat: no-repeat !important;
    background-position: 0 8px !important;
    background-size: 25px 17px !important;
}

/* Der neue zusätzliche Eintrag: Privater Modus unter dem Tab entfernt */  
.private-browsing-indicator-with-label {
    display: none !important;
} 

.tab-background {
border-radius: 8px 8px 0px 0px !important; border-image: none !important;
}
.tab-line {
display: none;
}

.tab-close-button {
color: red !important;
}