Hello,

Please add this code instead to the Theme Settings > Custom CSS > Global:

.wd-nav-vertical > li.shopbytool > a {
    padding:12px 0 12px 80px;
    background-image: url(https://www.minervatooldesign.com/wp-content/uploads/2021/04/toolbox.png);
    background-repeat: no-repeat;
    display:block;
    min-height:45px; 
    min-width:100px;
    background-size:25%;
    background-position:5%
}

Best Regards