yo ya tengo ocupado el userchrome.css con un script para agrandar la barra de marcadores asi que no se donde colocar el texto de esta modificacion en el paso 10:



/* Source file github.com/MrOtherGuy/firefox-csshacks/tree/master/chrome/multi-row_bo made available under Mozilla Public License v. 2.0
See the above repository for updates as well as full license text. */

/* Makes bookmarks toolbar span multiple rows */

#PersonalToolbar{
--multirow-bmb-n-rows: 3; /* Control how many rows are shown before scrolling */
--multirow-bmb-row-margin: 2px; /* Control how much spacing is between rows */
max-height: none !important;
}

#PlacesToolbar > hbox{
display: block;
width: 100vw;
}

#PlacesToolbarItems{
display: flex;
flex-wrap: wrap;
/*…   » ver todo el comentario