Eurorack is very cool and I totally understand the appeal of having physical devices to interact with but one thing I never understood is how you can recreate a specific configuration you liked later. Do you manually document every connection? Or just take pictures?

Once it's gone it's gone. That's part of what I like about analogue modular synthesizers. It's a liberating approach to doing music if you embrace it for what it is.

Neither, you just tell people about how great it was. Ideally, you don't record it either so that you can filter out the less imaginative people from your social circle. If challenged, you explain that you've moved on to a more abstract aesthetic, a musical plane which requires greater levels of commitment to attain.