8. Adding Columns: Power Query Add Column Tab and DAX Calculated Columns
8.7 Duplicate Column
Add Column › Duplicate Column copies the selected column as Column - Copy. Use it before a destructive change when you still need the original, for example duplicate Order DateTime and then turn the copy into Order Hour with Transform › Time › Hour.
Ravindra Bagale's Tip
Mitrano, khup students duplicate a column to "keep a backup" and then load both into the model. If you duplicate a column to transform it, remove the original (or the copy) before loading so the model doesn't carry the same data twice. Ekdum simple aahe, fakt savay lavun ghya.