Chapter is frequently filled in in my library, though not actually shown in the output style I use.
Volume refers to which volume the source itself is within a multivolume publication (e.g., “vol. 2 of Some Book”), while Series Volume refers to which number in a monograph series the publication has (sometimes including all of its individual volumes, sometimes each volume separately).
Ideally, I’d have two separate fields: Subseries Title and Subseries Volume – which would ideally not be any of the Custom fields, since those are sometimes used for various other things.
An example of a source could have the following:
_Reference type: _Book section
Year: 2019
Author: Martínez-Rodríguez, Elena
Title: Anatolian kinship word-pairs and their Mesopotamian connection
Editor: Adiego, Ignacio-Javier; Trabazo, Virgilio García; Vernet, Mariona; Obrador-Cursach, Bartomen; Martínez-Rodríguez, Elena
Book Title: The Luwic dialects and Anatolian: Inheritance and diffusion
Chapter: 7
Pages: 181-203
Series Title: Barcino Monographica Orientalia
Series Volume: 12
Subseries Title: Series Anatolica et Indogermanica
Subseries Volume: 1
In other words, the article is written by Elena Martínez-Rodríguez and appears as chapter 7 in the book The Luwic dialects and Anatolian (edited by Adiego et al.), which is volume 12 of the series Barcino Monographica Orientalia and volume 1 of the series Series Anatolica et Indogermanica (which is a subseries of Barcino Monographica Orientalia). This would then, in my output style, be bibligraphised thus:
Martínez-Rodríguez, Elena. 2019. Anatolian kinship word-pairs and their Mesopotamian connection. In Ignacio-Javier Adiego et al. (eds.),_The Luwic dialects and Anatolian: Inheritance and Diffusion_(Barcino Monographica Orientalia 12, Series Anatolica et Indogermanica 1). 181–203.
It would be so nice if it were possible to add arbitrary fields of one’s own, rather than being limited to eight Custom fields shared by all EndNote users, but used differently by all of them too. For example, I use Custom 1 for Original Year (in the case of reprinted/republished titles), and I had to delete a fair amount of data to clean up that field for this use – quite a few sources had various other types of data in that field, which I had to get rid of.