userChrome.css

/* Hide unwanted menu items */
#context-navigation, #context-sendimage, #context-setDesktopBackground, #context-openlink, #context-openlinkprivate, #context-bookmarklink, #context-sep-sendlinktodevice, #context-sendlinktodevice, #context-sendpagetodevice, #screenshots_mozilla_org-menuitem-_create-screenshot, #spell-separator, #spell-check-enabled, #context-sep-sendpagetodevice, #bookmarksMenuItemsSeparator {
    display: none !important
}

/* Darken unselected tabs */
#TabsToolbar #tabbrowser-tabs .tabbrowser-tab:not([selected]) .tab-content  {
  background-color: #d4d5da !important;
}

/* Tab hover gradient */
#TabsToolbar #tabbrowser-tabs .tabbrowser-tab:hover:not([selected]) .tab-content {
  background: linear-gradient(to bottom,#aaaaaf, #c4c5ca) !important;
}

/* Hide colored tab lines */
.tab-line {
  opacity: 0 !important;
}

/* Make the tab separators into full height borders */
.tabbrowser-tab::before,
.tabbrowser-tab::after{
border-left: 1px solid #a4a5a9  !important;
border-radius: 1px 1px 0px 0px !important;
margin-top: 0px !important;
margin-bottom: 0px !important;
opacity: 1 !important;
}

/* Add a border to the left of the first selected tab */
.tabbrowser-tab[visuallyselected]:first-of-type{
  border-left: 1px solid #a4a5a9 !important;
}

/* Add a grey border to the right of the last unselected tab */
.tabbrowser-tab:not([selected]):last-of-type::after{
border-left: 1px solid #ecedf3  !important;
border-radius: 1px 1px 0px 0px !important;
}

/*Add a grey border to the left of the first unselected tab*/
.tabbrowser-tab:not([selected]):first-of-type{
  border-left: 1px solid #ecedf3 !important;
  border-radius: 1px 1px 0px 0px !important;
}

/* Adjust bookmarks toolbar height*/
#navigator-toolbox #PersonalToolbar {
   min-height: 23px !important;
   margin-left: -5px !important;
}

/* Hide close button on last tab */
.tabbrowser-tab[first-visible-tab][last-visible-tab] .tab-close-button {
  visibility: collapse !important;
}

/* Move new tab button a tiny bit to the left*/
#new-tab-button {
    margin-left: -1px !important;
}



/* Remove hamburger button */
#PanelUI-menu-button {display: none !important;}

/*Replace dull grey bookmark folder icon with a nice colorized gold version */
 .bookmark-item[container] {
  list-style-image: url("data:image/png;base64,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") !important;
}

/******** Begin tabs on bottom tweak ********/

/* Toolbar order (start) ************************************/
#print-preview-toolbar,
#printedit-toolbar,
#titlebar {
  -moz-box-ordinal-group: 0 !important;
}
#navigator-toolbox #toolbar-menubar {
  -moz-box-ordinal-group: 1 !important;
}
/* navigation toolbar */
#navigator-toolbox #nav-bar {
  -moz-box-ordinal-group: 2 !important;
  background-color: #ecedf3 !important;
}
/* bookmarks toolbar */
#navigator-toolbox #PersonalToolbar {
  -moz-box-ordinal-group: 3 !important;
}

/* 3rd party toolbars */
#navigator-toolbox toolbar {
  -moz-box-ordinal-group: 10 !important;
}
/* tabs toolbar */
#navigator-toolbox #TabsToolbar {
  -moz-box-ordinal-group: 100 !important;
}
/* Toolbar order (end) **************************************/

/* Tab height */
#tabbrowser-tabs,
#tabbrowser-tabs > .tabbrowser-arrowscrollbox,
.tabbrowser-tabs[positionpinnedtabs] > .tabbrowser-tab[pinned] {
    min-height: 30px !important;
    margin-top:1px !important;
}

/* Adjust padding of toolbars to accommodate tabs on bottom */
#main-window:not([chromehidden*="toolbar"]) #navigator-toolbox {
    padding-bottom: 32px !important;
}

/* Fit tabs and toolbar to the current width of the window */
#TabsToolbar {
    position: absolute !important;
    bottom: 0 !important;
    width: 100vw !important;
}
#tabbrowser-tabs {
    width: 100vw !important;
}

/* Tabs toolbar adjustment */
#main-window[tabsintitlebar] #toolbar-menubar[autohide="true"][inactive="true"] ~ #TabsToolbar,
#main-window[tabsintitlebar][sizemode="maximized"] #toolbar-menubar[autohide="true"][inactive="true"] ~ #TabsToolbar,
#main-window[uidensity=compact][tabsintitlebar] #toolbar-menubar[autohide="true"][inactive="true"] ~ #TabsToolbar,
#main-window[uidensity=compact][tabsintitlebar][sizemode="maximized"] #toolbar-menubar[autohide="true"][inactive="true"] ~ #TabsToolbar,
#TabsToolbar{
  -moz-padding-start: 2px !important;
}
#main-window[tabsintitlebar][sizemode="normal"]:not([inFullscreen]) #TabsToolbar {
  margin-top: 0px !important;
}

/* Remove color overlay for lw-themes */
#main-window[style*='--lwt-header-image'] :-moz-any(#nav-bar,#PersonalToolbar,#TabsToolbar):-moz-lwtheme{
    background: unset !important;
}

/* Remove toolbar borders */
#main-window #navigator-toolbox::after {
  opacity: 0 !important;
}
#TabsToolbar{
  margin-bottom: 0px !important;
  border-bottom: 1px solid #a4a5a9 !important;
}
#main-window:not([inFullscreen="true"])[tabsintitlebar] #TabsToolbar{
  -moz-margin-end: 0px !important;
}
#main-window[tabsintitlebar] #TabsToolbar .titlebar-placeholder{
  visibility: collapse !important;
}
#main-window[tabsintitlebar][sizemode="normal"] #toolbar-menubar[autohide="true"][inactive="true"],
#main-window[tabsintitlebar][sizemode="maximized"] #toolbar-menubar[autohide="true"][inactive="true"] {
  margin-top: 21px !important;
}
#tabbrowser-tabs .tab-drop-indicator {
  margin-bottom: 0px !important;
}
#PersonalToolbar:-moz-lwtheme,
#nav-bar:-moz-lwtheme {
  background-image: none !important;
  box-shadow: none !important;
  border-top: none !important;
  border-bottom: none !important;
}

/* Remove vertical shift when dragging tabs*/
#navigator-toolbox[movingtab] > #titlebar > #TabsToolbar {
    padding-bottom: unset !important;
}
#navigator-toolbox[movingtab] #tabbrowser-tabs {
    padding-bottom: unset !important;
    margin-bottom: unset !important;
}
#navigator-toolbox[movingtab] > #nav-bar {
    margin-top: unset !important;
}

/* Hide non-required items that break tab position */
#TabsToolbar .private-browsing-indicator,
#TabsToolbar #window-controls,
#TabsToolbar *[type="caption-buttons"],
#TabsToolbar *[type="pre-tabs"],
#TabsToolbar *[type="post-tabs"] {
    display: none !important;
}

/************ End tabs on bottom tweak  *************/