FrameMaker currently allows only column-based footnotes.
Academic and other arenas often use very different footnote standards. For instance, it is common to have "running" footnotes. They look like a single paragraph with footnote reference numbers for each entry. Another common style is a fixed number of footnote columns that does not correspond with the number of text columns, e.g., three columns for footnotes, but two columns for text.
Footnotes often roll back to "1" with reference to sections or even individually numbered paragraphs rather than when the page increments. So para 2.3 might have three footnotes, numbered 1, 2, & 3, followed by para 2.4 with footnotes 1 & 2.