By default linked thumbnails are displayed ungrouped and in alphabetical order. Using the 
button the thumbnails can be grouped by:
- Folder
- Month
- Year
- Filetype
- Filename
The result for sorting by month is shown below.
This information applies to version 4.0.23 and later.
As of version 4, there are additional grouping options:
Unlike previous grouping, rank is set manually on each thumbnail.
Modified 10/05/2018 by alexhorridge