To add circle before navigation text in Squarespace, like this:
You can use this code to Custom CSS box.
div.header-nav-item>a:before {
content: "";
width: 10px;
height: 10px;
display: inline-block;
border: 2px solid #fff;
border-radius: 50%;
margin-right: 5px;
position: relative;
top: -2px;
}
div.header-nav-item>a {
align-items: center;
display: flex;
}
div.header-nav-item--active>a:before, div.header-nav-item>a:hover:before {
background-color: #fff !important;
}