Adding custom fields in the customers' profile is one of our top product feature requests. This way, it would be possible to import and map the customers' data with custom fields from Excel.
We've already been sending feedback about this. Rest assured I'll send yours as well. Also, our Product Developers Team are working on adding it in our future releases.
On the other hand, you can manually edit each customer info instead:
If you've got more questions, please let us know. We are here to help.