QB DESKTOP: If we export our customer list to Excel, change the sales reps and import back into QB - will it update the current Estimates we have for these customers to the new sales reps ? If not, how do we update our current Estimates without going one by one by one. 

AND WHY WHY WHY WHY WHY don't email addresses show on the invoice screen or the estimates screen?? No you can't add them in layout designer. You can add for PRINT but not for SCREEN. It is 2021. We NEED this. I have been asking Intuit to add this simple thing for 18 years.