Thumbnails can be sorted using a variety of criteria:
<ol>
<li><b>Modification Time:</b> when the file was last modified, according to its
metadata (where available) or according to the filesystem (as a fallback).</li>
<li><b>Checked State:</b> whether the file is marked for download.</li>
<li><b>Filename:</b> the full filename, including extension.</li>
<li><b>Extension:</b> the filename's extension. You can use this to group jpeg and
raw images, for instance.</li>
<li><b>File Type:</b> photo or video.</li>
<li><b>Device:</b> name of the device the photos and videos are being downloaded
from.</li>
</ol>