Temporary solution for titlebar buttons when using Mica

/* show titlebar buttonbox when mica is activated */
:root[tabsintitlebar] {
  @media (-moz-windows-mica) {
    &:not([lwtheme]) {
      @media not (-moz-windows-accent-color-in-titlebar) {
        & .titlebar-buttonbox {
          opacity: 1 !important;
        }
      }
    }
  }
}

/* set height to the buttonbox container */
.titlebar-buttonbox-container {
  height: 29px !important;
}

/* showing and hiding icons, not for private browsing mode */
#main-window:not([privatebrowsingmode="temporary"]) {
  .titlebar-close:not(:hover) > .toolbarbutton-icon {
    opacity: 0 !important;
  }

  .titlebar-max > .toolbarbutton-icon,
  .titlebar-min > .toolbarbutton-icon,
  .titlebar-restore > .toolbarbutton-icon {
    opacity: 0 !important;
  }
}

/* all padding and width fixes for 100% display scale */
:root[sizemode="normal"] .titlebar-close {
  padding: 7px 18px 9px 16px !important;
  width: 45px;
}

:root[sizemode="normal"] .titlebar-max {
  padding: 7px 18px 9px 16px !important;
}

:root[sizemode="maximized"] .titlebar-close {
  border-right: 2px solid transparent !important;
  background-clip: padding-box;
}

:root[sizemode="maximized"] .titlebar-close {
  padding: 7px 17px 9px !important;
}

:root[sizemode="maximized"] .titlebar-min {
  padding: 8px 17px 8px !important;
}

.titlebar-restore {
  padding: 7px 17px 9px !important;
}

/* optional: classic windows colors */
.titlebar-close:hover {
  background-color: #c42b1c !important;
  stroke: white !important;
}