Users can merge/join segments that were previously split into two or more sub-segments. In other words, you cannot merge two main segments (e.g. segment 5 with segment 6), however, you can merge one main segment (e.g. segment 5) with its sub-segments (e.g. 5-2, 5-3, etc.) or you can merge one sub-segment with another sub-segment that belongs to the same main segment.