textfont
is a Dict:
textfont = Dict{Symbol, Any}(:family=>"sans serif",
:size=>18,
:color=>"#ff7f0e")
but inside a trace definition you can give it as an attr
(attribute):
tr = scatter(x=1:5, y=rand(3:9, 5), mode="markers+text",
text = ["Aaaa", "Bbbbbb", "Ccc", "abccc", "lmnop"],
textfont =attr(family="sans serif",
size=18,
color="#ff7f0e"),
textposition="top")
pl = plot(tr, Layout(width=600, height=500))