Symptom:

In File Explorer with large icon view and in File Explorer preview pane, for the EMB files that were saved in e4, their design thumbnails are in high resolution against a colored background, while for the EMB files that were saved with earlier versions of EmbroideryStudio/DecoStudio, their design thumbnails are out of focus, in low resolution against a white background. For the machine file format, such as DST files, they do not show design thumbnails or design information at all.

Solution:

You must browse the design file folders with Design Library in e4 first, in order to get the design thumbnails created. Once it is done, all design thumbnails are back to normal including machine file formats when browsing design files with File Explorer.