[ownedbycats]

I use Action Chains' single-field edit to populate a custom column, #kobopath:

program:

# Returns 'Fanfiction/Fandom' tag for fanfics
	if $$#fanficcat then
		list_re($tags, ',', '^Fanfiction.(.*)$', 'Fanfiction/\1')

# Returns 'Kobo' for Kobo store books
	elif '\[Kobo Store\]' in $#kobostatus then 'Kobo Store' 

# Returns 'PDF' for PDFs
	elif $formats == 'PDF' then
		'PDF'

# Returns 'Loans' for Loans
	elif 'Loans' in $#vls then
		'Loans'

# Returns booktype for others
	else
		$#booktype

	fi

Then fit that into the send-to-device path (see here for why I'm using a re):

{#kobopath:re(_,/)}/{author_sort:sublist(0,1,&)}/{title} - {authors}

The main thing is that I can't remember how (or if even possible) to make a GPM template output the results of a single-function template. It may be easier to make separate chains for each template-type.