My Goldendict Qt Style.

qt-style.css

/* WARNING: hides all separators! */ 
#navToolbar::separator {
  width: 0px;
  margin: -3px;
}

/* Another way to hide specific separators */
#navToolbar #beforeOptionsSeparator, #navToolbar #beforeScanPopupSeparator, #navToolbar #afterScanPopupSeparator, #navToolbar #separatorBeforeZoom, #navToolbar #separatorBeforeSave {
  background: rgba(0,0,0,0%);
  width: 0px;
  margin: -3px;
}

/* Hide various buttons in the toolbar: */
#navToolbar #menuButtonXX, #navToolbar #soundButtonXX, #navToolbar #backButton, #navToolbar #forwardButton, #navToolbar #zoomInButton, #navToolbar #zoomOutButton, #navToolbar #zoomBaseButton, #navToolbar #saveArticleButton, #navToolbar #printButton {
  width:   0px;
  height:  0px;
  margin:  -3px;
}

/* remove the main toolbar handle */
#navToolbar::handle {
  image: none;
  width:  0px;
  margin-left: 1px;
}

#navToolbar #scanPopupButton {
  margin-left: 5px;
}

/* Colored header for the "Found in Dictionaries:" pane */
#dictsPaneTitleBar {
  background: lightblue;
  margin: 2px;
}

/* Thin separators between the main UI and sidebars */
QMainWindow::separator {
     width:  1px; /* when vertical */
     height: 1px; /* when horizontal */
}