The feature of “field substitution” is great but the options open to do this are too limited. One example: many electronic journals do not have pages anymore, but a code for the page. It would be nice to replace the field “page” by that code when the field “page” is empty.
I see 2 ways to implement this in Endnote (at least at the level of the user interface):
in the dialog box “field substitution”, add a selectable field next to the check box, so that we can replace the preselected options with a field name (or a combination of fields) and add a field “condition” (= empty, <> xxx, =any)
introduce a new separator in the definition of the styles. Currently, you use “|”. How about using “||” to signify either one or the other if the previous one is empty?