I am using imakeidx to generate a multicolumn index with makeindex.
Here is an excerpt from my .ind:
\item \BRbooktitlestyle {\BRepistlenumberstyle {1}Jean} \subitem \BRchapterstyle {2}\BRchvsep \BRversestyle {2} \dotfill \textrm{18} \subitem \BRchapterstyle {4}\BRchvsep \BRversestyle {9}\BRvrsep \BRversestyle {10} \dotfill \textrm{18} where \BRfoo are bibleref formatting macros. Unfortunately, the \item is at the bottom of a left column, so the \subitems get pushed to the right column:

Is there an equivalent to \nobreak which could be used here to prevent this behaviour, and how?
\makeatletter\g@addto@macro\@idxitem\nobreak\makeatotherin your preamble.