Firefox userChrome tweaks for Windows and macOS

userChrome.css

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); /* set default namespace to XUL */


window, page, dialog, wizard {
	color: -moz-DialogText;
	font: "SF Pro Text" !important;
}
:root:-moz-lwtheme-darktext {
    --url-and-searchbar-background-color: #fff;
    --chrome-background-color: #E3E4E6;
    --chrome-color: #18191a;
    --chrome-secondary-background-color: #F2F2F2 !important;
    --toolbox-border-bottom-color: #cccccc;
    --chrome-nav-buttons-background: #ffffff;
    --chrome-nav-buttons-hover-background: #E4E4E4 !important;
    --chrome-nav-bar-controls-border-color: #ccc;
    --chrome-selection-color: #000000 !important;
    --chrome-selection-background-color: #B3D8FD !important;
    --chrome-color: black；
    --toolbox-border-bottom-color: #E2E2E2;

}

/* Remove unnecessary buttons and the blank areas at left and right */
#tabbrowser-tabs .scrollbutton-up, #tabbrowser-tabs .scrollbutton-down, 
#alltabs-button, .tabbrowser-tab:not([fadein]), 
.titlebar-placeholder[type="pre-tabs"], 
.titlebar-placeholder[type="post-tabs"] {
  display: none;
}
.tabbrowser-tab:not([pinned]) {
  min-width: 140px !important;
  max-width: 225px !important;
}

.tabbrowser-tab[pinned] .tab-background,
.tabbrowser-tab[pinned]:hover .tab-background {
  display: none;
}
.tabbrowser-tab[pinned]::after {
  opacity: 0 !important;
}
.tabbrowser-tab[pinned]{
  position: relative;
}
.tabbrowser-tab:not([pinned]):not([pending]) {
  border-left: 1px solid #aaa !important;
}
.tabbrowser-tab:not([pinned]):not([pending]) + .tabbrowser-tab {
  border: 0 !important;
}

.tabbrowser-tab[pinned] {
  opacity: .5;
  transition: .2s;
}
.tabbrowser-tab[pinned]:hover,
.tabbrowser-tab[pinned][selected] {
  opacity: 1;
}


/* new shizzle */
#titlebar {
  margin-bottom: -30px !important;
}
#navigator-toolbox {
  display: flex;
  flex-direction: column;
}
#nav-bar {
  order: 0;
  height: 32px;
}

#nav-bar-customization-target {
  width: calc(100% - 170px);
}
/* osx... */
@media not screen and (-moz-windows-theme) {
  #nav-bar-customization-target {
    width: calc(100% - 100px);
    margin-left: 70px;
    margin-right: 30px;
  }
}
#PanelUI-button {
  position: absolute;
  top: 3px;
  right: 140px;
}
/* osx... */
@media not screen and (-moz-windows-theme) {
  #PanelUI-button {
    right: 0;
  }
}
#TabsToolbar {
  order: 1;
  max-height: 28px !important;
  box-shadow: 0 1px 0 #aaa;
}
#tabbrowser-tabs {
  max-width: calc(100% - 30px);
  height: 28px;
}
.tab-line {
  opacity: .2;
}
#toolbar-menubar {
  order: 2;
  display: none; /* no thx */
}


#main-window {
  border: 0;
}

#sidebar-header,
#sidebar-search-container {
  display: none !important;
}


.tabbrowser-tab:not([pinned]) .tab-close-button {
  display: -moz-box !important;
}