Reduce Open Document File Sizes From LibreOffice

By default, LibreOffice will generate and embed a thumbnail inside OpenDocument files (.odt, .ods, etc.). This thumbnail can take up a lot of extra space, especially for smaller files. Without the thumbnail, ODT files are more space efficient than DOCX files.

The option for generating a thumbnail can be disabled in the settings. To disable generating and embedding thumbnails in a file, open the menu:

Tools → Options... → LibreOffice → Advanced

Then click the button for `Expert Configuration`.

Select the preference named: `org.openoffice.Office.Common/Save/Document/GenerateThumbnail`

Double clicking on it toggles the value to `false`.

That's it!