Actually, both digital and analog cables matter. In fact, the cable at your source (the digital one) matters more because if you skimp on that, your expensive analog one further downstream will simply be a waste of money.
At first I was like you and believed digital cables don't make a difference anyway and had always just used whatever I could find around my computer desk. I had always just stole the cable from my portable USB harddrive and used it for my DAC (the same DAC as you, the Pico.) But one day I was also using the harddrive so I need a different one for the DAC, so I just grabbed another cable from a cheap USB hub and connected it to the DAC. Now I noticed the sound was different. Vastly different. I thought there was something wrong with my system. I couldn't believe it was the USB cable, but that was the only thing changed. So I waited for the USB harddrive to free up, so that I could rob its cable again and use it for the DAC. Voila. Everything is back to the way it was. Both cables were no more than 1 meter long, but the harddrive cable is of course built much better and thicker, with the cheap USB hub cable thinner and more flimsy, same as the ones you would find in a dollar store.
So until you get a decent USB cable for your system that isn't limiting what your DAC can offer, getting a good analog cable will just be futile. At least you won't be well prepared to judge accurately what different analog cables will give you.