How can you make .mkv files show a thumbnail with VLC player?

To make .mkv files show thumbnails in VLC Media Player, you can enable the thumbnail generation feature in the settings. Open VLC, go to "Tools" > "Preferences," select "Input/Codecs," and ensure that the "Show thumbnail" option is checked. Additionally, you may need to enable the "Use the following directory for thumbnail cache" option and specify a folder. After adjusting these settings, restart VLC, and the thumbnails should appear for your .mkv files.