Hi Rosewater, always nice to see that I am not the only one getting frustrated every now and then. Indeed this could/should have been an easy process by now. Even more so because the bits and pieces are already in place. Meaning:
So why Mendix has not taken that extra step and extended Studio Pro with the option to upload an (well-prepared) Excel document into your application and merge that into one or more entities and their associations. Seems like low hanging fruit to me. Hope they will do that one day.
Meanwhile, your 16 hours would probably have been better spent if you used new.mendix.com, created an application based on the excel that you have. Then exported your stuff in a module and imported that module into your app. Hope that works for you.
Hi Rosewater, I think you can follow these steps to create entity from Excel-Spreadsheet
https://academy.mendix.com/link/paths/75/Build-an-App-from-an-Excel-Spreadsheet
Hope it help.