“Open in default app” and “Show in system explorer” both use the same generic arrow icon, so users have to read the labels to tell them apart. These options currently only appear on the context menu for images.
Use the actual OS icons instead: the File Explorer icon for “Show in system explorer,” and the default app’s icon (e.g. Windows Photos for images) for “Open in default app.”
Works in File explorer, three-dot kebab menu, and note tab right-click.
You might have to adjust this in the case that a plugin (if plugins can) adds menu items to that or another group with the same data-section name. Or if you use a plugin to change the order of your menu options.