Use Hierarchical Facets
To use hierarchical facets in Predictive Merchandiser, do the following:
Select fields to facet in the Facets query pipeline stage.
In the Apply Rules query pipeline stage, select Field Name and Field Delimiter to use. This assumes a facet selected in Step 1 can be separated according to a delimiter, for example
Predictive Merchandiser’s facet zone can now display child facets in an expandable list.