Move text to top in cell merge

.top-text {
   vertical-align: top;
}
 
.top-text>div {
   margin-top: 8px;
}

var columns = [
   ...skip...
   {
     name: "Gender",
     fieldName: "Gender",
     width: "40",
     header: {
       text: "Gender",
       styleName: "orange-column"
     },
     mergeRule:{
       criteria: "value"
     },
     styleName: "top-text" //<====== Specify CSS
   },
   ...skip...
];