Hi there,
Inside custom.css add these classes below:
.YourClassName table:not(.show-first) tr >td:nth-of-type(1):before {
content: "";
position: absolute;
height: 20px;
width: 20px;
border: 1px solid #eee;
background: #fff;
}
.YourClassName table:not(.show-first) tr.selected >td:nth-of-type(1):after,
.YourClassName .mx-templategrid-item.selected table:not(.show-first) tr > td:nth-of-type(1):after {
content: "\2713";
color: #e8ae4b;
position: absolute;
font-size: 15px;
}
and you can customize it as you like