ThunderBird headers – remove lines & customize & smaller

Thunderbird email pane headers are taking too much space for many users. Unfortunately, as it’s common, in many cases, huge softwares lack the essential things..

so, the custom way to minimize the header

is the following way:

1. open Tools > Settings > Config Editor , then search & set toolkit.legacyUserProfileCustomizations.stylesheets to true
2. Go to %appdata%\Thunderbird\Profiles\<YOUR_PROFILE.deafult-esr>  and create location chrome\userChrome.css
3. In that file, insert:

#msgHeaderView {
    line-height: 0.85em;
}
#mail-notification-top {
    position:absolute; 
    right:0px; 
    width:550px; 
    height:10px!important;
    font-size:0.8em;
}
.header-buttons-container {
    display: none!important;
}
#messageHeader {
    display:flex!important;
    flex-direction: row;
}

5)  Restart thunderbird and headers pane should be very small