I do wonder if this belongs in annotations though. I think of infinite lines as annotating a plot versus representing data. It's too bad gallery entries cannot show up in two locations.

I've also pondered where to put this. It's not clearly an existing category - if one would create a new I'd do something like "Decorations" but I don't think it's worth creating that category right now. I've decided against "Text, labels and annotations" because that section has a strong focus on text, and annotations there are something (often again a text) local next to a data point. Both concepts do not apply to infinite lines, and I did not want to add a new interpretation of "annotation" in. I've therefore gone with matching the pure type "line". No solution is optional here, but I believe it's good enough.

I don't have any strong objections to it being here. I do think some of the things we do to annotate plots should be in the annotation section, but again, could be cross referenced.

It's too bad gallery entries cannot show up in two locations.

Tag it w/ it's secondary purpose? .. tag:: component:annotation or make a new label ..tags:: purpose: decorations though decorations that highlight information are usually annotations in visualization literature.