Hover Shadow

.sqs-block-button-element:hover {
  box-shadow: 0 5px 15px rgba(45, 45, 45, .4);
  //add any color
}

Add this code to the CSS panel.

You may replace the class with:
.sqs-button-element—primary

.sqs-button-element—secondary

.sqs-button-element—tertiary