I learned yesterday (here):
Keyword input types are specialized for compilation (this is different from the “method specialization” where you write multiple methods with varied positional arguments)
The functions in the Conditional Formats tests make extensive use of a mixed set of keywords to control the formatting options. There are very many combinations of different keywords possible. I guess this means that almost every invocation of each function will need compiling separately. I modelled this (very loosely) on my experience with Makie.jl.
Maybe there is a more efficient way?