Is it possible to add stuff to the markup based on condition?
Like in this example, when I want to add td only on the first iteration (only for the first elemen         
        
Yes, AngularJS has 2 directives for this occasion:
At the end of the day both solutions will give the same visual effect but the underlying DOM structure will be different. For simple use cases ng-show / ng-hide is probably OK, but larger portions of the DOM should be treated with ng-switch.
For the use case from this question I would advice using ng-switch.
The best solution should be:
<tr ng-repeat="m in myData">
   <td>{{m.Name}}</td>
   <td>{{m.LastName}}</td>
   <td ng-if="$first" rowspan="{{myData.length}}">
       <ul>
           <li ng-repeat="d in days">
               {{d.hours}}
           </li>
       </ul>
   </td> 
</tr>