Jancy uses CSV (comma-seperated value) files as file format for proxies. You’ll probably want a good CSV editor as you create/modify these files. While Excel and Google Sheets seems like a natural choice because both can work with CSV files, you might be better off using software built specifically for CSV files. Software, like Excel, are very sophisticated data manipulation tools and, if you don’t prevent them, they’ll try and guess what type of data is in each cell. When they write the data back to the CSV file you’ll find values, like credit card numbers, looking much different. There are plenty of good CSV editors on the internet. Here’s a couple if you don’t want to spend time looking: