Hi Diego! Currently in gspread_pandas.spread.Spread().df_to_sheet() you are limited to either wiping the sheet or overwriting existing rows using the replace parameter. How feasible would it be to add an option to append to an existing sheet instead of just overwriting when replace = False? Based on some googling, I think the answer probably lies in values_append within gspread.
If you can get me pointed in the right direction I'll see if I can put together a PR.