The DOM tree is a bit confusing. Actually it's a mess. There's no easy way to identify the refresh line in the widget menu for each of them.
I've found a work-around until I figure it out.
Instead of dragging in a specific data container, put it into a named block. That block is what the user should drag in. Next, in that block, drag in an HTML item, a reprompt button, and another HTML item.
HTML Item1: <div name="myRepromptButton" style="display:none">
HTML Item2: </div>
When you run the report, that button should not be visible.
Now, drag in the blocks you want into the dashboard.
Create a new report, it will contain a single HTML item:
<script>
var reprompts = document.getElementsByName('myRepromptButton');
setInterval( function() {
for (var i=0;i<reprompts.length;i++){
reprompts[i].firstChild.firstChild.click();
}
, 1800000)
</script>Drag that empty looking report into the dashboard and wait for 30 minutes (or if you're feeling impatient change that 1800000 to something smaller).