1. Table footnotes use a different numbering system than document footnotes, usually
Symbols like *, †, and ‡
Letters like a, b, and c, and
Numbers.

So designers must be able to create a unique numbering series for each table.

2. STEM-Govt publications often require table source notes. They look like footnotes, appear after the table, but don't have a unique symbol or number. Example:
Source: US Department of Agriculture.
* Table Footnote blah blah.

3. Table footnotes should be in the TFoot section of the table, essentially a part of the table itself. Designer should be allowed to format TFoot section to appear with or without borders, use a different font or paragraph formatting style, and control spacing before/after the last visible row.

4. In most cases, the TFoot section should span the entire width of the table. Essentially a row with one merged cell. But allow the designer to adjust this.

5. The footnote reference in the table body should be automatically hyperlinked to its table footnote. A fully accessible hyperlink with <Reference> and <Link> / <Link-OBJR> tags.

6. @titanium9 's comment about Framemaker's tables is correct. Was teaching tables in FM in 1986 ... 34 years ago. I don't understand why InDesign doesn't have such capable table tools.

Adobe FrameMaker has been doing real table footnotes attached to the table correctly for about a quarter century now (long before Adobe bought it). There is no question Adobe knows what a real table footnote is, and how to implement it well.

After 20 years of asking for real table footnotes in InDesign with no success it's pretty clear the FrameMaker team holds the InDesign team's leash... at least regarding this one small but important feature.

At least the FrameMaker team is allowing the InDesign team to implement table footnotes horribly. Better than nothing.

Real table footnotes will come to InDesign when FrameMaker dies, but that will likely be long after you do. FrameMaker is a minor but apparently profitable product for Adobe, who just invested in a total 64 bit rewrite of it for the 2019 version.

I support this request. I suspect my (in-house) customers are going to insist I continue to “fake” table footnotes, so that they can use a different numbering system – typically a, b, c – and place table footnotes immediately after the table.

I think table footnotes should be in the table footer section of the table so that:
1) They are part of the table, not the rest of the page content, and
2) They automatically repeat at the bottom of multi-page tables.

Right now, as folks have said, the table footnotes are separated from the actual table itself.

For accessibility, the footnote <Note> tags would be in the <TFoot> section within the <Table> tag.

Yes! Our documents are 100% done with table footnotes, so the current feature for footnotes doesn't work for us AT ALL!

Agreed Klaas - they must sit immediately under the relevant table to make sense.

Yes, I'd like to have this feature too. The current solution does not fit my usual workflow

Yes, please. The CC2019 version is doing its job only halfway.