Yeah,
I think toml is great short/simple config files, yaml is good for medium length/complexity, and I have yet to see anything that’s not painful for long config files.
After normalizing, one could get to a tidy heterogeneous solution.
(Only the finest vaporware spoken here.)
In a tiny yaml file it's pretty easy to understand what everything is; it's huge files where toml's forcing you to full qualify nested tables becomes useful.
Too many huge yaml files where I'm just scrolled somewhere in the middle and have no clue what part of the tree I'm actually looking at.
I think yaml files hold's up well to about 50 lines.
I have only seen toml files up to about 10-20 lines and it looks great at that scale, but I am having a hard time imagining it being nice at 500+ lines.