[gibxxi]

Hi, looking at backing up my whole system to transfer to son's shield TV. He has an old 1st attempt metadata collection which I want to update but don't want to overwrite his viewed content. Have backed up and ready to update his but want his already played list to remain the same. Any way please?

I believe 'watched status' is what your referring to, and in this case it will be saved in Kodi's video DB. One thing you can do is exclude the DB from the backup, which you probably ought to do anyway if the sources / paths of the media differ on his tablet than on your other system (i.e different content paths, or different protocols like SMB vs. NFS vs. AirPlay, etc.).

Another way to preserve watched status would be to setup individual TRAKT.tv accounts for yourself and your son prior to restoring your backed up config to his tablet, then install the Kodi TRAKT addon and configure it to sync your respective EXISTING libraries with the TRAKT.tv website (and your accounts therein) each time a library update has concluded. That way even if the database gets hosed, you can always do a fresh install, re-setup the TRAKT.tv addon and pull back in all your already synced watched statuses.

Once the watched statuses for each of your respective libraries / systems have been initially synced with your respective (seperate) TRAKT.tv accounts, then you can proceed to restore your backup to his tablet. I would still exclude the database itself since your metadata will be replacing his, but once TRAKT is setup, you can always rescrape the library content in short-order and have the TRAKT add-on restore the watched-status of the rescraped content. With this in mind however it may pay to also exclude the TRAKT.tv addon and it's settings folder from the backup, or ensure the configuration is switched to his account from yours post-restore.

Sounds a lot more complicated than it is, the way i've written this, but I do a similar trick for library sharing between multiple systems, retaining watched status across them all. The moral of this long and involved story is TRAKT is more useful than simply telling the world what you've recently watched (as in my signature). It also serves as a backup of your valuable watched statuses, and the official add-on (in the kodi repo) is highly configurable. It's notifications can be mildly annoying, but these can be turned off if so desired.