ggplot2多行标题，不同的缩进

我正在为出版物生成图形，我希望能够在ggplot本身中标记图形的面板（而不是导出到发布者等），以便它们在最终文档中整齐地排列在一起。我想通过在标题中添加字母（“ A”）来尝试执行此操作，但是我希望标题居中，并且希望字母在左上角。

# base graph:

ggplot(iris, aes(x = Sepal.Length, y = Sepal.Width, color = Species, shape = Species))+
  geom_jitter(size = 6.5)+
  ggtitle("A \n \n The Actual Long, Normal Title of Titliness")+
  theme(plot.title = element_text(hjust = 0.5, face = "bold", size = 30),
        axis.ticks = element_blank(),
        legend.text = element_text(size = 25),
        axis.title = element_text(size = 25, face = "bold"),
        axis.text = element_text(size = 25, vjust = 0.05),
        legend.position = "bottom")

现在，如果我愿意通过手动间隔每个标题来“伪造”它，我可以使它起作用，但是这似乎很耗时且很粗糙。

# sloppy solution
ggplot(iris, aes(x = Sepal.Length, y = Sepal.Width, color = Species, shape = Species))+
  geom_jitter(size = 6.5)+
  ggtitle("A \n \n             The Actual Long, Normal Title of Titliness")+
  theme(plot.title = element_text(hjust = 0,face = "bold", size = 30),
        axis.ticks = element_blank(),
        legend.text = element_text(size = 25),
        axis.title = element_text(size = 25, face = "bold"),
        axis.text = element_text(size = 25, vjust = 0.05),
        legend.position = "bottom")

有没有一种方法可以分别调用标题的每个“行”以获取其自身的正当值？

还有其他创意解决方案吗？

Also, I saw potential in mtext (Splitting axis labels with expressions), but couldn't figure out how to implement it with ggplot2 (vs base plot function.. it seems like they're not compatible). This post was all sorts of interesting (Multi-line ggplot Title With Different Font Size, Face, etc), but I am still new to R and I couldn't figure out how to edit this clever stuff to change indentation.

Thanks!