Mit diesem Code funktioniert das dann hier:
#titlebar {
-moz-box-ordinal-group: 100 !important;
}
/* space above tabs toolbar */
#main-window[tabsintitlebar][sizemode="maximized"] * #titlebar {
margin-top: -8px !important;
}
/* space for menubar above navigation toolbar (Firefox titlebar) */
#main-window[tabsintitlebar]:not([sizemode="fullscreen"]) #nav-bar {
margin-top: 40px !important;
}
#main-window[tabsintitlebar][sizemode="maximized"]:not([sizemode="fullscreen"]) #nav-
bar {
margin-top: 6px !important;
}
/* add 'drag' feature to space above navigation toolbar */
#main-window[tabsintitlebar] #navigator-toolbox,
#main-window[tabsintitlebar] #nav-bar {
-moz-window-dragging: drag !important;
}
/* move menubar to the top and extend its with to full window width */
#toolbar-menubar {
position: fixed !important;
width: 100vw !important;
-moz-window-dragging: drag !important;
}
/* move menubars / tab toolbars caption buttons to windows top right position */
#main-window[tabsintitlebar]:not([inDOMFullscreen="true"]) .titlebar-buttonbox-container {
position: fixed !important;
right: 0 !important;
visibility: visible !important;
display: block !important;
}
/* menubar postion after moving to the top */
#toolbar-menubar {
top: 10px !important;
}
/* Linux/macOS */
/* space above navigation toolbar (OS titlebar) */
/* set to '0', if no menubar is used */
#main-window:not([tabsintitlebar]):not([sizemode="fullscreen"]) #nav-bar {
margin-top: 18px !important;
}
/* menubar postion in maximized mode after moving to the top */
#main-window[tabsintitlebar][sizemode="maximized"] #toolbar-menubar {
top: 0px !important;
}
/* caption button position in maximized mode after moving to the top */
#main-window[tabsintitlebar]:not([inDOMFullscreen="true"]) .titlebar-buttonbox-container,
#main-window[tabsintitlebar][sizemode="maximized"]:not([inDOMFullscreen="true"])
.titlebar-buttonbox-container {
top: 4px !important;
}
/* Windows */
@media (-moz-os-version:windows-win10), (-moz-os-version:windows-win8), (-moz-os-
version:windows-win7) {
/* set to '0', if no menubar is used */
#main-window:not([tabsintitlebar]):not([sizemode="fullscreen"]) #nav-bar {
margin-top: 8px !important;
}
/* set to '0', if no menubar is used */
#main-window[tabsintitlebar][sizemode="maximized"]:not
([sizemode="fullscreen"]) #nav-bar {
margin-top: 4px !important;
}
#main-window[tabsintitlebar][sizemode="maximized"] #toolbar-menubar {
top: 8px !important;
}
#main-window[tabsintitlebar]:not([inDOMFullscreen="true"]) .titlebar-buttonbox-
container {
top: 0px !important;
}
#main-window[tabsintitlebar][sizemode="maximized"]:not
([inDOMFullscreen="true"]) .titlebar-buttonbox-container {
top: 8px !important;
}
}
/* hide line above navigation toolbar appearing in some cases */
#main-window:not([tabsintitlebar]) #nav-bar,
#main-window:not([tabsintitlebar]) #navigator-toolbox {
border-top: 0 !important;
box-shadow: unset !important;
}
/* tweaks for fullscreen mode */
#main-window[tabsintitlebar][sizemode="fullscreen"] * #TabsToolbar {
-moz-padding-start: 0px !important;
}
/* tweaks for fullscreen mode */
#main-window[tabsintitlebar][sizemode="fullscreen"]:not([inDOMFullscreen="true"])
.titlebar-buttonbox-container,
#main-window[tabsintitlebar][sizemode="fullscreen"] #toolbar-menubar[autohide="true"] ~
#TabsToolbar .titlebar-buttonbox-container,
#main-window[tabsintitlebar][sizemode="fullscreen"] #navigator-toolbox #PanelUI-button,
#main-window #TabsToolbar #window-controls {
display: none !important;
}
/* hide non-required items */
#TabsToolbar .private-browsing-indicator,
#TabsToolbar #window-controls,
#TabsToolbar *[type="caption-buttons"],
#TabsToolbar *[type="pre-tabs"],
#TabsToolbar *[type="post-tabs"] {
display: none !important;
}
/* Windows 7 extra tweaks */
@media (-moz-os-version: windows-win7) {
@media all and (-moz-windows-compositor) {
#main-window[tabsintitlebar]:not([inDOMFullscreen="true"]) * .titlebar-
buttonbox-container {
display: none !important;
}
}
@media not all and (-moz-windows-compositor) {
#main-window[tabsintitlebar]:not([inDOMFullscreen="true"]) .titlebar-buttonbox-
container {
top: -8px !important;
}
#main-window[tabsintitlebar][sizemode="maximized"]:not
([inDOMFullscreen="true"]) .titlebar-buttonbox-container {
top: 0px !important;
}
}
}
/* Windows 10 extra tweaks */
@media (-moz-os-version: windows-win10) {
#main-window:not([tabsintitlebar]) menubar > menu:not

-moz-lwtheme):hover:not
([disabled="true"]),
#main-window:not([tabsintitlebar]) menubar > menu:not

-moz-lwtheme)[_moz-
menuactive="true"]:not([disabled="true"]) {
background-color: Highlight !important;
color: HighlightText !important;
}
}
/* disable Mozillas tab jumping nonsense when moving 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;
}
Du wirst dir aber bestimmt alle Abstände selber raussuchen müssen, damit das dann so aussieht: