Increase margins of common legend from ggpubr

I am trying to increase the size of the margins of a common legend built when using ggarrange. I could increase the width of the plot, but I do not really want to do that. What do you suggest?

    data1_df = data.frame(x = 1:4, y = 5e-6, type = 'type1')
    data2_df = data.frame(x = 1:4, y = 6e-6, type = 'type2')
    data3_df = data.frame(x = 1:4, y = 8e-6, type = 'type3')
    data4_df = data.frame(x = 1:4, y = 9e-6, type = 'type4')

    dataDF = NULL
    dataDF = rbind(dataDF,data1_df)
    dataDF = rbind(dataDF,data2_df)
    dataDF = rbind(dataDF,data3_df)
    dataDF = rbind(dataDF,data4_df)

    
for(i in 1:4){

plotG = ggplot(dataDF,aes(x = x, y = y, color = type, shape = type))+
  geom_line(aes(group = type),show.legend = F)+
  geom_point(aes(group = type),size = 3)+
  scale_color_manual(breaks = c("type1","type2","type3","type4"), 
                     values = c("darkorange3","lightblue3","skyblue1","dodgerblue3"))+
  scale_shape_manual(breaks = c("type1","type2","type3","type4"), 
                     values = c(3,16,17, 18))+
  xlab('test')+ylab('Slope (= 1/4 * Va)')+
  theme_bw()+ggtitle('Time 3')+
  guides(color = guide_legend(byrow = TRUE), shape = guide_legend(byrow = TRUE))+
  theme(legend.key.spacing.y = unit(0.5, "cm"))

assign(paste0('plot',i),plotG)
}
  
final_plot = ggarrange(print(plot1), print(plot2), print(plot3),print(plot4), labels = c("A","B","C","D"), ncol = 2, nrow = 2,common.legend = TRUE,legend = 'right')

You can increase the margins around the legend box using the legend.box.margin theme option:

library(ggplot2)
library(ggpubr)

for (i in 1:4) {
  plotG <- ggplot(dataDF, aes(x = x, y = y, color = type, shape = type)) +
    geom_line(aes(group = type), show.legend = F) +
    geom_point(aes(group = type), size = 3) +
    scale_color_manual(
      breaks = c("type1", "type2", "type3", "type4"),
      values = c("darkorange3", "lightblue3", "skyblue1", "dodgerblue3")
    ) +
    scale_shape_manual(
      breaks = c("type1", "type2", "type3", "type4"),
      values = c(3, 16, 17, 18)
    ) +
    xlab("test") +
    ylab("Slope (= 1/4 * Va)") +
    theme_bw() +
    ggtitle("Time 3") +
    guides(color = guide_legend(byrow = TRUE), shape = guide_legend(byrow = TRUE)) +
    theme(
      legend.key.spacing.y = unit(0.5, "cm"),
      legend.box.margin = margin(l = 2, r = 2, unit = "cm")
    )

  assign(paste0("plot", i), plotG)
}

ggarrange(print(plot1), print(plot2), print(plot3), print(plot4), labels = c("A", "B", "C", "D"), ncol = 2, nrow = 2, common.legend = TRUE, legend = "right")