I think there may be an easier way to accomplish what Joerg has in mind. The documents I write in Word and then place into InDesign have two types of footnotes. One type I think of as "author footnotes." Those are footnotes that I write. InDesign numbers those in sequence. But I often include quotations from judicial opinions that have what I think of as "court footnotes," and those should retain the footnote number that the court gave them rather than being renumbered automatically by InDesign.

I think there is a straightforward way to accomplish this. InDesign's current footnote style includes a counter. The counter begins at 1. Each time the user adds a footnote, the counter increments by 1, so InDesign knows what number to give the next footnote. (If the user deletes a footnote, the counter decrements by 1.) And that's great, as far as it goes. Of course, if I add a "court footnote," the counter also increments by 1, and that messes things up. For example, I have a file with "author's notes 1, 2, 3, and 4 at the beginning. Then it has a court footnote that the court has numbered "2." The court footnote should get the number "2" in the InDesign file, but InDesign's automatic footnote numbering will give it "5." If I add a footnote of my own later, InDesign will number it "6," but really it is only author's footnote 5. So ideally, the sequence of notes I have described should look like 1, 2, 3, 4, 2, 5. InDesign cannot now do that.

If you created a second footnote style, it would add the flexibility that InDesign now lacks. The second footnote style should differ from the existing one in two ways: (1) If the user selects the new footnote style, InDesign should ask the user what number (or other designation, such as an asterisk) the new footnote should have. (2) Adding the footnote this way should not affect the counter on InDesign's existing footnote style.

That's all there is to it. author's footnotes would continue to get sequential numbers from InDesign's existing footnote style. Court (or other footnotes from quoted material) would get special numbers that the user assigns. Then InDesign would have no difficulty with a footnote order like the one above: 1, 2, 3, 4, 2, 5.

This is not an original idea with me. Microsoft Word has exactly this feature already, although I don't know how Microsoft had coded it. Now I am no admirer of Microsoft; over the years its programs have become less and less user friendly, which finally drove me to learn and primarily use Linux. But publishers want documents in Word format.

If Adobe decides to do this, I think it would be cheap and easy. You can take most of the coding for the existing footnote type (placement at the bottom of the page, indents, etc.) and use it for the new footnote style, simply omitting the counter and asking the user to designate the symbol for the new note. InDesign's existing footnote style, when the user invokes it, would continue to number the author's footnotes sequentially, as it should.

InDesign already has multiple paragraph and character styles. Why not multiple footnote styles?

Also, there is an editorial convention for the order of reference symbols (Australian Style Manual https://www.stylemanual.gov.au/referencing-and-attribution/documentary-note). I have used these in legal journals. Also, as noted here, they are particularly useful when typesetting equations for print so as to avoid misreading it as a superior exponent number.

* (asterisk)
† (dagger)
‡ (double dagger)
§ (section sign)
# (hash sign)

Restart the symbols on each page. If you have more than five notes on a page, double the symbols (**, ††).

Yes. We have clients that want footnotes sequenced in order across the entire document (not restarted at each section or chapter) as well as clients that have different footnotes for tables on a page that might have other footnotes related to the narrative on the same page.

At the very least, it would be helpful to have the ability to tell all footnotes not to restart at a particular section/chapter, or to tell an individual footnote to start at a particular number. Even though my checkbox to restart at every page/spread/section is not checked, it still restarts. It seems that if you want footnotes to never restart but to continually increment across the whole document, you have to thread every thing together which is a huge problem if you have section dividers or other pages between chapters and the client adds/removes text causing everything to reflow.

This is really very necessary! In some texts, it is necessary to preserve the original footnotes of, say, another edition or author’s footnotes, and there is a need to add footnotes of another context, say the reviewer's footnotes. And these two footnote contexts should somehow differ markedly. At the same time, the publisher wants both those and others to remain on the same page.

... and very important, too:
telling the footnote text where to go.

Means for multi-column text, e.g. 2 columns:
The numbers 1 to 3 are placed in column 1, numbers 4 to 8 in column 2 - all (!) footnote text is placed in column 2 (from the bottom).

Or even the same like above, but placing the footnote text only in column 1 (from the bottom)

etc.

I have so many jobs where the footnotes have to be manually placed because the described is not possible.

If the developers have access to »Advent 3B2« (I worked with about 10 years ago for a company: a layout program with text and graphics mixing environment; renamed to » Arbortext Advanced Print Publisher, APP«; http://gpsl.co/technology/ptc-arbortext/app/), they should take a look (or get the manual if possible) - very powerful in terms of footnotes and marginalia management etc. ... as a source of ideas determined very inspiring.

Regards
Joerg