packageVersion("ggplot2")
# '3.5.2'

library(ggplot2)

p <- ggplot(mpg) +
  geom_point(aes(x = factor(cyl), y = displ, color = hwy)) +
  scale_color_fermenter(palette = "RdYlBu", direction = 1) +
  theme(legend.key.width = unit(0.25, "lines"))

plots <- list(
  p + ggtitle("default"),
  p + ggtitle("0.5 lines") + theme(legend.key.height = unit(0.5, "lines")),
  p + ggtitle("2.5 lines") + theme(legend.key.height = unit(2.5, "lines")),
  p + ggtitle("null") + theme(legend.key.height = unit(1, "null"))
)

cowplot::plot_grid(plotlist = plots)

# in fresh session

remotes::install_github("tidyverse/ggplot2")
packageVersion("ggplot2")
# '3.5.2.9000'

library(ggplot2)

# same plotting code as above