I’m trying to change the style of the button, I want a triangle made with CSS to appear but when I paint it it shows two triangles.

Yes, it allows me to show only one button at the ends, but the style I apply is not the one I want.

::-webkit-scrollbar-button {
    display: none;
}

::-webkit-scrollbar-button:single-button:vertical:decrement {
    display: block;
    height: 20px;
    background-color: transparent;
    border-style: solid;
    border-width: 0 20px 20px 20px;
    border-color: transparent transparent #007BFF transparent;
}

::-webkit-scrollbar-button:single-button:vertical:increment {
    display: block;
    height: 20px;
    background-color: transparent;
    border-style: solid;
    border-width: 20px 20px 0 20px;
    border-color: #007BFF transparent transparent transparent;
}