Usually layer sorting make sense only when you have a mosaic with overlapped layers. For a better mosaic you may wish to bring to the front the layers that are more similar to your main theme image i.e layers with better "score". This can be done with special menu option Menu Layers - Sort on Score Asc.

You may see The Score for individual layers at Right Click Pop Up menu.

In some situation you probably may want to bring poor scored layers to front for easier deleting or replacing them. Use menu option Menu Layers - Sort on Score Desc for that

Please see these examples of sorting usage:
  
Layers were not sorted:
 
Layers were sorted on best score:
Layers were not sorted
 
Layers were sorted on best score
 
Below are the real life example. This is the same mosaic before and after sorting. Left mosaic image is not sorted, right image have sorted layers:

Before Layer Sorting.  After Layer Sorting.