It appears that Endnotes are either single-column or paragraph form; no option for varying column numbers.
If this is true, I feel this is not sufficient. At least half, if not more, of scientific publications use 2 columns in the references (even if there is only one in the main body of the paper). This saves space because so many references are short, while retaining the readability afforded by having each number-note on a single line. I request this be added.
If there was a simple way to change to fixed content at the very end, when the paper is done, it wouldn't be so bad; but on reading about your macro for searching and changing the reference numbers, I'm leery of attempting that; certainly not more than once. And if there are any changes in the references that require re-editing after that has been done, then all the numbers would have to be changed in both the document and the Endnotes. This would be hell.
So I repeat my request: 2 or 3 column ought to be available, while still automatic. If they are and I've missed it, I promise to dance a little jig.

Steven Rowat