adding extra header to the table and wrap it to headers

[str_guru]

I have a function which creating a table like below and i want to add one more header to the table and merger the header at the first column.

i want to export this table to excel thats why looking for another solution , tried with flextable already

tbl_summmary <-
  tibble(
    outcome = c("A (%)", "B (%)", "C (%)", "D (%)", "Total (n)"),
    group_1 = c(.25, .25, .125, .325, 10),
    group_2 = c(.50, 0.0, .325, .125, 20),
    group_3 = c(.10, .40, .125, .325, 40))

tbl_summmary %>% as.data.frame()

output should be look like

[technocrat]

You want the gt package for presentation tables