I need to do something that seems like it should be simple in ggtree but I haven't been able to figure it out, and none of the examples in the documentation seem to be quite what I need.

I have a quite large tree (~5000 samples). In the paper I am going to show the full tree to show high-level patterns, and then a few figures that zoom in on very small clades. In the big full tree, I want to add labels on ONLY the ancestral nodes of the clades that I'm going to highlight later, to show where they are in the tree. So I want some kind of annotation where I can specify geom_something(node=1234, label="A") + geom_something(node=4321, label="B") or something along those lines. All of the documentation I can see for annotating nodes seems to require you to label every node. I don't want to use geom_cladelabel or geom_hilight because the clades are so small relative to the whole tree that they're not really visible when highlighted that way. I just want to be able to reference particular nodes in the tree. Any help would be appreciated!