For normal Tinderbox users, this is done by adding the following to the container’s $OnAdd action. This is most easily editable in Inspector > Action Inspector > Action:

$DisplayExpression='$SiblingOrder + ". " + $Name';

However, if you are using BoxPress, the procedure is much simpler—and safer, since it does not interfere with the other elements in the BoxPress SmartExpression. Just set the $OnAdd action to this:

$DENum=1;

That’s it!