правило overflow блокирует выпадающее меню

CSS Сайдбара
/* ------------------------------ SIDEBAR-20-TWO-1 ----------------------- */
.SIDEBAR-20-TWO-1 {
    background-color: rgba(142, 229, 238, 0.8); /* CadetBlue2 */
    border-left: solid grey 1px;
    display: flex;
    flex-direction: column;
    float: left;
    justify-content: space-between;
    max-width: 20%;
    position: fixed;
    padding: 0.5em 0 0.5em 0;
    top: 60px;
    bottom: 0;
    left: 80%;
    right: 0;
    overflow-y: scroll;
}
.div-nav-menu_ITEM-SECTION-1_sidebar-20-two-1 {
    display: inline-block;
    font-size: 1em;
    line-height: 1em;
}
.ul-nav-menu_ITEM-SECTION-1_sidebar-20-two-1 {
    font-size: 0.5em;
    display: block;
    line-height: 1.5em;
    list-style: none;
    padding: 0 0 0 10px;
}
.item-nav-menu_ITEM-SECTION-1_sidebar-20-two-1 {
    cursor: pointer;
    padding: 0.3em 0.3em 0.3em 1em;
    text-decoration: none;
    justify-content: flex-end;
}
.item-nav-menu_ITEM-SECTION-1_sidebar-20-two-1:hover {
    background-color: rgba(54, 54, 54, 0.7); /* grey21 */;
    color: white;
    padding: 0.3em 0.3em 0.3em 1em;
}




/* ---------- div-nav-menu_ITEM-SECTION-2_sidebar-20-two-1 ---------- */
.div-nav-menu_ITEM-SECTION-2_sidebar-20-two-1 {
    padding: 5px 0 0 0;
}
.ul-nav-menu_ITEM-SECTION-2_sidebar-20-two-1 {
    font-size: 16px;
    display: block;
    line-height: 1.5em;
    list-style: none;
    padding: 0 0 0 10px;
}
.item-nav-menu_ITEM-SECTION-2_sidebar-20-two-1 {
    cursor: pointer;
    padding: 5px 5px 5px 5px;
    text-decoration: none;
}
.item-nav-menu_ITEM-SECTION-2_sidebar-20-two-1:hover {
    background-color: rgba(54, 54, 54, 0.7); /* grey21 */;
    border-radius: 5px;
    color: white;
    padding: 5px 5px 5px 5px;
}






CSS Выпадающего меню, которое находится в сайдбаре.
/* ---------- SIDEBAR-20-TWO-1 ---------- */
.dropdown_SIDEBAR-20-TWO-1 {
    display: inline-block;
    min-width: 100%;
    width: 150px;
    position: relative;
}
.dropdown-label_SIDEBAR-20-TWO-1 {
    display: flex;
    flex-flow: row wrap;
    font-size: 0.8em;
    justify-content: flex-start;
    padding: 0.3em 1em 0.3em 3em;
    cursor: pointer;
    border-bottom: solid rgba(156, 156, 156, 10) 1px; /* grey61 */
}
.dropdown-label_SIDEBAR-20-TWO-1:hover {
    background-color: rgba(54, 54, 54, 0.8); /* grey21 */
    color: white;
}
.dropdown-label_SIDEBAR-20-TWO-1::after {
    content: "";
    position: absolute;
    left: 1em;
    top: 1em;
    border: 0.3em solid;
    border-color: rgba(105, 105, 105, 10) transparent transparent; /* grey41 */
}
.dropdown_SIDEBAR-20-TWO-1:hover .dropdown-label_SIDEBAR-20-TWO-1::after {
    top: 0.7em;
    border-color: transparent transparent rgba(232, 232, 232, 10); /* grey91 */
}
.dropdown-menu_SIDEBAR-20-TWO-1 {
    background-color: rgba(142, 229, 238, 0.8); /* CadetBlue2 */;
    display: none;
    position: absolute;
    right: 100%;
    top: 0;
    min-width: 100%;
    width: 100px;
    z-index: 1;
}
.dropdown_SIDEBAR-20-TWO-1:hover .dropdown-menu_SIDEBAR-20-TWO-1 {
    display: block;
    border-radius: 5px;
}
.dropdown-sub-menu_SIDEBAR-20-TWO-1 {
    border-top: solid rgba(156, 156, 156, 10) 1px; /* grey61 */;
    border-left: solid rgba(156, 156, 156, 10) 1px; /* grey61 */;
    border-right: solid rgba(156, 156, 156, 10) 1px; /* grey61 */;
    font-size: 0.8em;
    list-style: none;
    z-index: 0;
}

.dropdown-sub-menu_SIDEBAR-20-TWO-1 > li + li {
;
}

.dropdown-sub-menu_SIDEBAR-20-TWO-1 > li > a {
    background-color: rgba(220, 220, 220, 10); /* Gainsboro */
    border-bottom: solid rgba(156, 156, 156, 10) 1px; /* grey61 */
    color: black;
    display: block;
    padding: 0.4em 1.5em;
    text-decoration: none;
}
.dropdown-sub-menu_SIDEBAR-20-TWO-1 > li > a:hover {
    background-color: rgba(54, 54, 54, 0.7); /* grey21 */;
    color: white;
    padding: 0.4em 1.5em;
}

 <!---------------------------------------- SIDEBAR-20-TWO-1 ---------------------------------------->
                <div class="SIDEBAR-20-TWO-1">
                    
                    <div class="div-nav-menu_ITEM-SECTION-1_sidebar-20-two-1">
                        
                        <div class="dropdown_SIDEBAR-20-TWO-1">
                            <div class="dropdown-label_SIDEBAR-20-TWO-1">FRONTEND</div>
                            <div class="dropdown-menu_SIDEBAR-20-TWO-1">
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                            </div><!--dropdown-menu_SIDEBAR-20-TWO-1-->
                        </div><!--dropdown_SIDEBAR-20-TWO-1-->
    
                       
                        
                        
                        
                        
                         </div><!--div-nav-menu_ITEM-SECTION-1_sidebar-20-two-1-->
                
                </div><!------------------------------------------side-bar-20-two------------------------------------------>