[pmennen]

I'm using Kodi 18.1 portable with the Estuary skin under Win10. After I watch a video from my collection, Kodi displays a checkmark next to the file name to indicate that the video has been watched. For me, this is pretty much an essential feature because I watch several TV series at once and without this feature, it would be quite difficult to figure out which episode is the next one to watch. Also sometimes I abandon a series and then decide to revisit it a year or more later. Especially in that situation, it would be quite time consuming to figure out where I had left off. BTW, I'm selecting the videos I want to watch from the Favorites menu rather than using a library, but I assume these checkmarks also appear when a library is used to navigate to the desired video. I would like to upgrade to Kodi 18.6 (or perhaps eventually 19.0) but I can't do this because I've learned from experience that any version upgrade will cause all the checkmarks to be cleared. So without some kind of workaround, I'm kind of stuck with version 18.1 forever. I was hoping there is a file somewhere that stores this information and that if I copy the file to the new installation then the watched videos will still be checked when using the updated kodi version. Is there such a file, or perhaps another way of solving this problem?  Thanks. ~Paul

[Karellen]

I've learned from experience that any version upgrade will cause all the checkmarks to be cleared.

Not true. The watched status should carry through... unless you have done a complete reinstall by deleting everything or you have installed to a different portable location, then of course they will be lost.

Is there such a file, or perhaps another way of solving this problem?

Watched status are saved in the database in the Files table.
You could also export your library to Separate files (NFO Files) and they are saved in the nfo files.
You could also use the Watched List add-on,
But as you are not using the library, your only option is the files table, which is unnecessary as they should carry through.

[Klojum]

but I can't do this because I've learned from experience that any version upgrade will cause all the checkmarks to be cleared.

Nope... Kodi upgrades can include a database upgrade, but checkmarks will not be cleared during that upgrade.

The data for the checkmarks of watched videos is in the MyVideo116.db SQLite database file.
There is the files table with the playCount field.
There is also the bookmark table with two timestamp fields for indicating the resume point in a video.