userChrome.css

/* square corners for context menu */
.tab-background,
#urlbar-background,
#searchbar,
menupopup,
.menupopup-arrowscrollbox{ border-radius: 0 !important; }
:root{--arrowpanel-border-radius:0px !important;}


#urlbar-background{
        background-color: white !important;
    }

#searchbar{
        background-color: white !important;
    }

#navigator-toolbox{ --toolbar-bgcolor: #F5F5F5; }    


.tab-background{
border-radius: 0px 0px !important;
margin-bottom: 0px !important;
background-color: lightgray;
}

.tabbrowser-tab{
    background-color: lightgray;
}

.tabbrowser-tab:not([selected=true]):not([multiselected=true]) .tab-background{
background-color: F5F5F5;
}

menupopup > menu, menupopup > menuitem{
padding-block: 2px !important;
min-height: 0px !important;
}
:root{
--arrowpanel-menuitem-padding: 2px !important;
}

#context-navigation,
#context-sep-navigation {
  display:none !important;
}