Hide QScrollBar arrows

If you need to hide just the arrows inside buttons then you can try to set background and border in this way:

QScrollBar::right-arrow:horizontal, QScrollBar::left-arrow:horizontal
{
      border: none;
      background: none;
      color: none;
}

If you want to hide whole buttons then you go with code below.

QScrollBar::add-line:horizontal {
      border: none;
      background: none;
}

QScrollBar::sub-line:horizontal {
      border: none;
      background: none;
}

I know this is an old question, but I've ran into an issue with this question's approved answer, and I've found a fix for it so I'm going to leave this here in case someone runs into the same problem that I did.

While the accepted answer suggests setting border, background and color to none, this only visually hides the scrollbar arrows. What I mean by this is that you can still click them, and the scrollbar's handle, while it can move to the place they occupied, can not be clicked on if your cursor is in the area the arrow buttons occupied.

To also functionally hide them, you should set their width and height styles to 0px as well. This will make it so you can click on the handle if the scrollbar's handle is in the area the arrow-buttons occupied.