Please enable markup (HTML tag) support for popup lists.
What kind of pop-up list do you mean? Can't tell from the cropped screenshot.
What creates it?
// show popup list
var cmd = clickData.func.command;
var dlg = clickData.func.Dlg;
dlg.choices = menu_items;
dlg.menu = 0;
dlg.Show();
That generates and shows a standard system menu, I think, which means markup isn't supported.