In the plot below I'd like to move the label "V-Engine" into the plot margin. Adjusting the nudge_x argument is moving the "S-Engine" label but not the "V-Engine" label. 
library(ggplot2)
library(ggrepel)
library(dplyr)
ds <- 
    mtcars %>%
    mutate(vs = factor(vs, labels = c("V-Engine", "S-Engine"))) %>% 
    # Create labels for the rightmost data points
    group_by(vs) %>% 
        mutate(
            label = 
                case_when(
                    wt == max(wt) ~ as.character(vs), 
                    TRUE ~ NA_character_
                )
        ) %>%
    ungroup() 
ds %>% 
    ggplot(aes(x = wt, y = mpg, color = vs)) +
    geom_smooth(se=FALSE) + 
    geom_label_repel(aes(label = label), nudge_x = 1, na.rm = TRUE) + 
    guides(color = FALSE) + 
    theme_minimal() + 
    theme(plot.margin = unit(c(1,3,1,1), "cm")) 

