How to add a button to mobile Header between logo and menu icon – Squarespace

Go to Design > Custom CSS > Paste the following code

/* Show button on mobile menu*/
@media screen and (max-width:1024px) {

/* show button */
.header-actions {
    display: block !important;
}
.header .header-actions-action--cta {
    display: block;
    width: 10% !important;
}

/* logo width */
.header-title-nav-wrapper {
    flex: 50% !important;
}
}