Preserve “zero” or support “index math” on the series index

First, let me say that I am rabidly in love with this plugin.
It is awesome. Truly. (So, thanks!)

I have a small request that would make life just a little easier, though
not by much — so it’s small. :__)

I have a large and growing series of posts in my Raja Yoga Insights series. (Currently at 12. Will be at 16 when it’s done.)

At some point, it became clear that a “series index” (a partial TOC, actually) would be a good idea. So I created one and gave it the number zero.

I expected it appear at the top, allowing me to keep notes on class #1 numbered as the 1st post in the series, which helps to keep me organized.

To my surprise, it showed up as the last post in the series. That’s fine, too. But when I save with the number zero, the zero is replaced with number at the end of the series — so the next post I make comes after the index, instead of before.

Ideally, of course, that number would stay as zero, and would always sort to the end.

Now, somehow I expect it will be really *hard* to implement something like that. So another option might be a formula like “+1” or something, which would allow a set of end-of-series posts to be added (+1, +2), while leaving room for an intermediate number of standard-series posts.

That too, would be pretty nearly impossible, I know. So it would understandably have to be a feature you pay for, or forget about it!

But then, maybe there is a feasible alternative that will occur to you. So I’m writing this message, mostly in case it sparks some useful idea.

In the meantime, the workaround is simple: Every time I update the index for the next article, I just have to remember to change the index number to zero, after which it will automatically move to the end of the series once again.

So, in addition to sharing my admiration for the plugin, this observation might make a useful addition to the documentation. (If it is already there, please accept my apologies!)
:__)

The page I need help with: [log in to see the link]