@footnotes {
  	margin-top: 6pt ;
  	margin-left: 0;
  	columns: 2 ;
    column-gap: 12pt;
  	column-fill: balance;
  	background-color: pink ;
  	}

I was expecting two columns in the footnote area. I am aware of

prince-column-footnote

however I couldn't find listed in the properties documentation.

I just wanted to see if the balance would come out better this way.

The real solution is inline footnotes. I see you have a lot on your plate before these occur.

Colors in the text are to show where and how much tracking has been added to the paragraph.

Jim Albright
Wycliffe Bible Translators

1. two-column footnotes.png‎ 69.2 kB

Yes, "float: prince-column-footnote" will work, but I don't think the @footnotes area can have multiple columns yet, and of course inline footnotes are still on the roadmap.