I recently installed Witcher III on a new computer and since I would like to have a copy for future installations I downloaded Witcher III (1.31) and all DLC's as setup files via GOG Galaxy.

I proceeded to install Witcher III via said setup-file, the the DLC's incl. HoS and BnW, plus the german language pack.

I then imported Witcher into GOG Galaxy. The game was corretly imported and runs perfectly fine, but GOG won't recognise the DLC's. It's not a problem just a nuissance that bugs me.

Is there a way to fix this wihout the need to download and install all files through the Galaxy client? (I would hate to DL another 35GB+ again).

Greetings,
RaEyE

If you downloaded manually, and you don't want Galaxy managing your installation, why do you use Galaxy? You don't need it to run the game.

As far as I know unchecking the DLCs and download them again with GOG Galaxy should only download the DLCs again and not the game+DLCs.
But if you do it you do it on your own risk. Galaxy is still in beta (alpha) and I deinstalled Galaxy long time ago.