In the browse.conf file, in this part:
ca_objects {
facets {
...
}
}
add this block:
lcsh_facet = {
type = attribute,
element_code = lcsh_terms,
group_mode = alphabetical,
order_by_label_fields = [name],
label_singular = _("LCSH term"),
label_plural = _("LCSH terms"),
description = _("Find objects according to LCSH terms."),
},
Save, purge cache files and try.