.select-checkbox option::before {
    content: "\2610";
    width: 1.3em;
    text-align: center;
    display: inline-block;
}

.select-checkbox option:checked::before {
    content: "\2611";
}
.header-hidden-checkbox::before {
    font-size: 16px;
    padding: 5px 10px 5px 5px;
    content: "\2610";
}
.header-visible-checkbox::before {
    font-size: 16px;
    padding: 5px 10px 5px 5px;
    content: "\2611";
}
.headers-container {
    max-height: 250px;
    overflow: auto;
}

.filter-headers {
    top: 55px;
    padding: 5px;
    opacity: 0.3;
    position: initial;
}

    .filter-headers:hover {
        opacity: 1;
    }
    .filter-headers:active, .filter-headers:focus {
       border: none;
       outline: none;
    }