I like this feature too!
categories_collapsed_name_template = '{first.sort:shorten(
10,'',0)} - {last.sort::shorten(
10,'',0)}'
categories_collapse_model = 'partition'
I tweaked the partition name lengths to 10 (from 4), which i think works well because you can see most words or names in full at that length.
imo - , it would be nice to be able to switch modes with a right click sub-menu on the section heading. So could switch between old view and partition view without going to tweaks (my 2cents)
nice job on all the other improvements in this version !!!