A few
custom ids/captions examples follow here:

.
Here is a footnote reference,[^1] and another[^longnote] and an inline footnote ^[it works!].

And then there are duplicate references to those footnotes here[^1][^longnote].

[^1]: Here is the footnote.

[^longnote]: This one will have a regular looking HTML `#ID` for a link, but the footnote itself will be called `longnote` (in superscript).

    Subsequent paragraphs are indented to show that they
belong to the previous footnote.
.
xxx
.


With a label override:
.
Here is a footnote reference,[^1] and another[^2 longnote text link acting as a footnote reference].

[^1 foo]: Here is the footnote.

[^2 bar]: While named `#fn-bar` in the HTML link, it's HTML `#ID` link will be `2` instead, thanks to the custom anchor and caption render methods.
.
xxx
.