The vertical splitters separate different groups of buttons (such as navigation buttons and social sharing buttons) on the Button Bar.
There are no configuration options which would allow you to remove the splitters but you could remove them completely by using the following CSS in your gallery's 'index.html' page:
<style type="text/css">
.jb-bb-splitter {
border-width: 0px;
}
</style>However, this may have an unwanted side effect, for example when wrapping the Button Bar on screens of limited width, where Juicebox will not be able to accurately calculate the width of the Button Bar. (It would expect the splitters to be there.)
Therefore, it may be safer to hide (rather than remove) the splitters by using the following CSS:
<style type="text/css">
.jb-bb-splitter {
border-color: transparent !important;
}
</style>The splitters are usually only 1px wide each so hiding them should not make much of a visible difference in your gallery.