Ich habe den Code von Aris  dazu etwas erweitert, ab Zeile 145.
 dazu etwas erweitert, ab Zeile 145.
CSS
		
					
				/* Firefox Quantum userChrome.css tweaks ************************************************/
/* Github: https://github.com/aris-t2/customcssforfx ************************************/
/****************************************************************************************/
@-moz-document  url-prefix(chrome://mozapps/content/extensions/aboutaddons.html) {
    .more-options-menu panel-item {
      background: white !important;
      color: black !important;
      margin: 0 1px !important;
      border: 1px solid lightgrey !important;
    }
    
    addon-list panel-item:not([badged]){
      border: 1px solid lightgrey !important;
    }
    
    addon-list addon-card:not([expanded="true"]) panel-list * {
      background: white !important;
      color: black !important;
    }
    
    @supports -moz-bool-pref("browser.in-content.dark-mode") {
      @media (prefers-color-scheme: dark) {
        addon-list addon-card:not([expanded="true"]) panel-list *,
        .more-options-menu panel-item {
          background: black !important;
          color: white !important;
      }
    }}
    
    addon-list panel-item{
      margin: 0 1px !important;
    }
    
    /* reduce size of default buttons */
    link:-moz-any([href$="panel-item.css"],[href$="panel-list.css"]) ~ button {
      width: unset !important;
      padding: 2px 5px !important; 
    }
    
    /* remove three dots button */
    addon-card .more-options-button {
      display: none !important;
    }
    /* remove button icon */
    addon-list panel-item {
      --icon: unset !important;
    }
    
    /* restore buttons */
    addon-list .more-options-menu :-moz-any(addon-options,plugin-options) panel-list {
      position: relative !important;
      display: block !important;
      overflow: hidden !important;
      margin-top: -25px;
      box-shadow: none !important;
      background: unset !important;
      border: unset !important;
      box-shadow: unset !important;
      min-width: unset !important;
      width: unset !important;
    }
    div.arrow.top + div.list {
      display: flex !important;
      flex-flow: row wrap !important;
      justify-content: flex-start !important;
    }
    panel-item[action="preferences"] {
      order: -1;
    }
    
    panel-item[badged] {
      border: 1px solid Highlight !important;
    }
    
    panel-item[badged]::after,
    :host([badged]) button::after,
    link:-moz-any([href$="panel-item.css"],[href$="panel-list.css"]) ~ button::after,
    :-moz-any(addon-options,plugin-options) button::after {
      display: none !important;
      content: unset !important;
    }
    
    addon-page-options panel-list {
      min-width: unset !important;
      width: auto !important;
      max-width: 300px !important;
      z-index: 1000 !important;
    }
    
    addon-page-options panel-list panel-item {
      min-width: 280px !important;
      width: 280px !important;
    }
    
    .sticky-container {
      z-index: 1000 !important;
    }
    
    link:-moz-any([href$="panel-item.css"],[href$="panel-list.css"]) ~ button label[accesskey] {
      padding-inline-start: 20px !important;
      padding-top: 3px !important;
      padding-bottom: 3px !important;
      min-width: 290px !important;
      width: 290px !important;
    }
    addon-page-options panel-list panel-item[accesskey][checked] {
      background: url("chrome://global/skin/icons/check.svg") 5px no-repeat !important;
    }
    
    
    addon-list addon-card:not([expanded="true"]) panel-list {
      position: absolute !important;
      display: block !important;
      overflow: hidden !important;
      box-shadow: none !important;
      background: unset !important;
      border: unset !important;
      box-shadow: unset !important;
      min-width: unset !important;
      width: unset !important;
      left: unset !important;
      top: unset !important;
      right: 46px !important;
      bottom: unset !important;
    }
    addon-list:-moz-any([type="theme"],[type="plugin"],[type="dictionary"]) addon-card:not([expanded="true"]) panel-list {
      right: 15px !important;
    }
    addon-list addon-card:not([expanded="true"]) panel-list {
      margin-top: -48px !important;
    }
    addon-list:-moz-any([type="theme"]) addon-card:not([expanded="true"]) panel-list {
      margin-top: -80px !important;
    }
    
    .addon.card {
       width: 1200px;
}
input[type="checkbox"].toggle-button {
    
    margin-right: 300px !important;
}
} 
		
		
	 
															
		










