Deleting too many named range - defined name manager not opening

I have seen an issue in my consultation where a customer had too many defined name, and could not open the defined name manager. This customer had over 500 thousands defined name. Basically a macro did create those defined name for him, and got stuck in a loop.

The customer wanted to keep it's data, but get rid of those defined name. The solution in this case was to create an new workbook and then move all the value of the cells (copy paste) and not the sheet. At the end, I find and replace any reference to the old workbook in my formula, and then bingo, my customer was able to keep all the data they had, and go on.