regarding timeline software, the following discussion may contain some further suggestions:

http://www.outlinersoftware.com/topics/viewt/2503/0/historical-timeline-modelling

I want to create a timeline/eventline to help plot a novel which is not
told in chronological order. I'm looking to create a purely
chronological eventline, as well as an a-chronological 'throughline'
with the scenes in the order in which the story unfolds, correlated with
parallel eventlines showing 'who-knows-what-when' for several
characters. I may end up using paper and markers, but I'd like to find
some software which would allow me to change things around freely
without facing the tedium of constant redrawing.

I'd take a look at this: http://sourceforge.net/projects/ostorybook/

It was a commercial product but has gone open source. It appears to be designed for exactly what you want to accomplish.

My sincere thanks to Dr Andus, Hugh, and CRC for your spot-on suggestions. It made my day to learn that such software is available. I've already poured over the online info on oStorybook and Aeon Timeline. Both look exceedingly capable, even beyond what I was imagining, and I look forward exploring them hands on.

When I find an additional parcel of unconflicted time I'll also minicrimp O4D. Beyond its event tracking function, I've become interested in the 'reverse outlining' usage Dr Andus has described. I chop text apart and rearrange it more than most I think, and I'd like to find a more efficient/pleasureable way to proceed than the typical cutting and pasting.

Definitely worth exploring Gingko, then (gingkoapp.com). But I'd much prefer it if they'd finally produce a separate app. Whether this will happen now, I don't know...

I just read Dr. Andrus' post here: https://drandus.wordpress.com/tag/storyview/

How have I possibly missed this gem of an outliner???

It's definitely aged but it looks like it is still one of the most powerful windows single-pane outliners availabe.

Is anyone still using it and know if it remains the best for this purpose?

It's not going to be updated anymore probably. If not minding the old gui look, considering what it does:

Collapsing / expanding levels with many related options, customized UI toolbars, multi monitor benefits etc, for large projects with the need to manipulate views fast to get overview and other benefits, still pretty unique. Has certain great uses.

Just gone on sale again (USD50.00) until Sept. 6, 2019