But it looks they are not stored, just installed, and then they're gone? In which place would I have to look for them? Thanks again!
I think they stick around somewhere or another? Maybe not. Either way, there are offline patches at en.thewitcher.com/community/
(scroll down to find them) that you can back up. I don't know why GOG doesn't provide links to these patches, but it definitely fits with their general "do as little as possible" approach to the game. For example, the "issues and solutions" sticky in this subforum is irrelevant and outdated by more than a year, and tons of solutions to common issues that were PMed to them never showed up anywhere. So yeah, can definitely see why you'd think that the autopatching is the only way to update.