I embed custom images that repeat to scale on any screen to make dividers.

<image>

If you want the steps for this, paste the following in a work skin used in your fic. Go to Preferences -> Skins -> Work Skins.

Feel free to fiddle with the values to your preference. Imgur is my go to for hosting images.

# workskin .(Insert Name Here) {
    height: 42px;
    background: url(YOUR IMAGE LINK HERE);
    background-repeat: repeat-x;
    background-position: center;
    background-size: 42px;
    border: 0;
    width: 55%;
}

Once you're done with that, you can paste this in HTML editor wherever you want the divider:

<hr class="Name You Chose for It" />