Two lists are presented, one above the other. The top list is a multiselectable list which indicates the classes to be merged. You may select more than one class in this list by pressing the "Shift" or "Ctrl" key simultaneously with your selection.
The bottom list indicates the class into which the classes from the top list will be merged. You may select only one class from the list.
After the selections have been made in both lists, pressing the "Merge" button will perform the operation. The "Merge" function affects the entire training channel and not only the portion that is loaded.