.bws-icon {
    position: absolute;
    display: block;
    left: @bws-sidebar-width;
    top: 114px;
    width: 40px;
    height: 40px;
    background: #bbbbbb url(/juju-ui/assets/images/browser_icon.png)
        no-repeat center center;
    box-shadow: 3px 0 2px rgba(0, 0, 0, 0.1);
    border-top-right-radius: 4px;
    border-bottom-right-radius: 4px;
}
.content-visible .bws-icon {
    left: @bws-sidebar-width + @bws-panel-width;
}

.bws-icon {
    position: absolute;
    display: block;
    left: @bws-sidebar-width;
    top: 114px;
    width: 40px;
    height: 40px;
    background: #bbbbbb url(/juju-ui/assets/images/browser_icon.png)
        no-repeat center center;
    box-shadow: 3px 0 2px rgba(0, 0, 0, 0.1);
    border-top-right-radius: 4px;
    border-bottom-right-radius: 4px;
    z-index: 10;
}
.content-visible .bws-icon {
    left: @bws-sidebar-width + @bws-panel-width;
}

Add a z-index to get the minimize button over the topology
Add a z-index to get the minimize button over the topology