This brings up the question of how Ludwig Wittgenstein arranged his own zettelkasten...

Peter Geach made an arrangement of Wittgenstein's zettels which was broadly kept in the edited and published version Zettel (1967). Apparently fragments on the same topic were clipped together indicating that Wittgenstein's method was most likely by topical headings. However there were also a large number of slips "lying loose in the box." Perhaps these were notes which he had yet to file or which some intervening archivist may have re-arranged?

In any case, Geach otherwise arranged all the materials as best as he could according to subject matter. As a result the printed book version isn't necessarily the arrangement that Wittgenstein would have made, but the editors of the book felt that at least Geach's arrangement made it an "instructive and readable compilation".

This source doesn't indicate the use of alphabetical dividers or other tabbed divisions.