Applies to- QuarkXPress 2018 on Mac OS and Windows OS.

Span Footnotes over Columns-

This option makes all the footnotes in the document span across the columns in a multi-column text frame.This option determines the distance between the last paragraph of one footnote and the first paragraph of the next footnote in a column. You cannot use a negative value.

How Span Footnotes works in QuarkXPress 2018?
Footnotes can be formatted to span across all columns. By default, footnotes will span across all columns and you can turn this off in Footnote Separator Style. The new option “Footnote Across Columns” introduced in below dialog. Footnotes for Spanned column paragraphs will be listed below along with other footnotes as spanned footnotes. For legacy version document, Footnotes Across Columns option will be unchecked by default.