You didn't need to 'smuggle' them, just let your western relatives bring them over the border, which was entirely legal (sending via postal service would have worked too, but I wouldn't have risked that tbh because all parcels from West into East were opened and sometimes content "mysteriously" disappeared).

The C64 wasn't affected by the COCOM embargo, so 'export' was legal from West Germany, and import into East Germany anyway. East German citizens who had access to D-Mark (again: western relatives were the key here) could also simply walk into an 'Intershop' and buy a Commodore or Atari 8-bitter. Finally there was also the so-called GENEX catalogue, which was a delivery service run by East Germany where West German citizens could directly buy both Eastern and Western products for hard currency and had them directly delivered to their East German relatives (including C64s):

https://www.spiegel.de/geschichte/genex-kataloge-der-sonderb...

16-bit computers were affected by the western COCOM embargo though. It was technically illegal to export a PC or even an Amiga from West Germany into East Germany. So if you wanted to bring an Amiga over the border that would technically be smuggling - in the sense of smuggling them out of West Germany, since that was the illegal part - I bet nobody gave a shit though since quite a few Amigas found their way into East Germany, they were just prohibitively expensive on the 'private market' (around 20..30k (East-) Mark, which was the equivalent of a higher end car - like a Lada 1500 - or about 3..4 years of a typical wage).