Yep, I ended up doing something similar, I however manage it with a Python script: whenever I save the Excel spreadsheet, a script is triggered that converts it to a TXT file. It then generates a random 10-character alphanumeric+char string and makes sure it did not get used previously for any note. It then assigns it to the new note. I then have a feedback loop so that the Excel file gets updated with this information. I found this to be the way to handle GUIDs for synonym with Anki.