library(tidymodels)

lm_mod <- parsnip::linear_reg() %>% parsnip::set_engine("lm")
wflow <- workflow() %>% add_model(lm_mod)

wflow_1 <- wflow %>% add_variables(outcomes = "mpg", predictors = c(wt))

outcome_names(wflow_1)
#> Error in UseMethod("outcome_names"): no applicable method for 'outcome_names' applied to an object of class "workflow_variables"