Excel should be able to do what you need, it just requires a slightly different workflow from what you might be used to:
1- save an *.xlsx file that is your "true" working file, which has column widths set and formatting and whatever else makes it easier to work with.
2- regularly File -> Save this file to avoid losing work.
3- when you're ready to export to the card generator, go to File -> Save A Copy, and then at the bottom of the save dialog, change the file extension from *.xlsx to *.csv. You may need to experiment to find the "right" csv; IIRC excel has three different csv options, you want the vanilla comma-delimited no-frills version.
4- if it asks you for options when saving the file, you want it to use commas to delimit, and " as the string indicator, and to use quotes on all columns if possible.
By using Save A Copy instead of save as, what is open in excel will always be the xlsx file, and you're just exporting a snapshot to csv at regular intervals.
It takes some adjustments to get used to, but since all spreadsheet programs are a giant piece of #$&*@!, this is the best workflow I've found yet.