[davidfor]

No, that is for calibres use, not the devices. Calibre maintains a file called metadata.calibre in the root directory of the device. This is a link between the books on the device and the library. It is used to speed up the matching of books on the device to the library. And to help where there are some issues with that matching. Some ereader apps, such as KOReader, will look at this for metadata, but, I do not know of any dedicated ereader device that does.

How the metadata on an is store for display is different for each of the devices. Most are using some sort of database on the device. The device processes the books when they are first seen and update a database of some sort with the metadata. Kobos does this in a batch when you disconnect the device. Kindles do it in the background. I don't know about the others.

As you list that you have a Kobo Libra H2O, then it will process the book the first time it sees it and extract the metadata. If the book is replaced, and the device deems that the book has change (basically the file size has changed), the device will clear the metadata for the book and process it as a new book. When this happens, you lose the reading status, annotations and collections for the book. That is what happens if you manually put the book on the device. If you change a book and manually put it on the device in the same location and file name, the updated metadata and cover should be seen.

If you use calibre's send-to-device function, there is a lot more that can happen. The KoboTouch driver, can side step some of this. The default configuration for the driver is to send replacements to the device so that the device will not see it as a new book. This means you can fix things like spelling and styles or the cover in a book, and it will not affect the reading status or any annotations. This is an option in the driver and can be turned off. This is the default for historical reasons and because I believe it is the more desirable setting.

The driver can also directly directly update the metadata in the database on the device. This is how it sets the series information for the books (Kobo does not read the series info from the sideloaded books). It can also update all the other metadata the device displays to match any changes made in the calibre library. The series info update is on by default, but the rest is off by default (again, history of the driver). This can happen automatically when the device is connected.

If you use the KoboTouchExtended driver, it inherits the above function from the KoboTouch driver, but, it needs to be configured separately.

In short, if you use calibre and change the metadata in a book and then resend it to a Kobo device, the metadata you see on the device will be updated.

If you don't want the driver to update things automatically, my Kobo Utilities plugin can do it for selected books while the device is connected. And it has finer control over what it updates. And a lot of other functions.

As you mention the author sort, Kobo does not use this at all. It expects the author to be in the format "FN LN", and for multiple authors, "FN1 LN1, FN2 LN2". It works out the sorting from that. It works for most cases, but, it doesn't take into account names like "John von Trapp". That will sort as "Trapp, John von" (which might be right depending on nationality).