Firefox Proton quick tab fix

userChrome.css

.tab-background {
    margin-top: 1px !important;
    margin-bottom: 1px !important;
    border-radius: 0 !important;
}

.tabbrowser-tab {
    padding: 0 !important;
}

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

:root {
    --tab-toolbar-navbar-overlap: 0px !important;
    --tab-min-height: 2.5em !important;
}

:root #tabbrowser-tabs {
    --tab-min-height: 2.5em !important;
}

#TabsToolbar {
    height: var(--tab-min-height) !important;
}