I think you used be able to create a section to contain footnotes in columns, but it seems you can only select within one footnote now.
Is it still possible to have footnotes arranged in columns (main text without columns)?
I don’t remember any such possibility.
Footnote area is part of page “contents”, i.e. space needed for notes is borrowed from this “contents” area. On the contrary, header and footer are set apart for “contents” and can have their own layout, column-wise (insert a section).
Basically, “contents” and footnote share the same layout: single-column text => single-column note zone, multi-column text => same multi-column area. In addition Writer will do its best to position the note in the same column as its anchor.
I tried to insert a 2-column section in the footnote area, but it is totally ineffective. In the case of an already multi-column page, it creates a huge havoc with text jumping apparently randomly to next column or becoming invisible.
So, it could only work with endnotes.
Yes because endnotes are listed in their own page style. Yet, there are many “glitches” with endnotes as the page management is not as standard as one could expect.