Thank you @ChrisRackauckas, I will try add the plt::Plot argument to the argument list and see what happens, even though I don’t understand what is happening under the hood.
In terms of documentation, I feel it was written by the authors to the co-authors. As someone coming from outside, a normal user, I can’t catch up easily, which is paradoxical since one of the goals of Plots.jl is to “just work” out of the box with no need to memorize syntax nor function prototypes. I think a lot of the attention in the docs has been put into the internal machinery and less on the available customization options, makes sense?
Anyways, I wish I could understand the API more to document it myself, but this is a chicken or egg problem: I don’t understand enough to document, there is no documentation to understand.