Cascading LookApp is part of KWizCom Forms App (Professional edition).
The KWizCom Cascading LookApp is a SharePoint Online add-in that enhances your existing Lookup columns with added capabilities:
KWizCom Cascading LookApp
Supports Cascading fields ("City" filtered by "Country")
Enables the filtering of the displayed items in the lookup field according to a view defined in the target list
Cross site lookup - enables the creation of lookup field for lists that are located on different sites.
Enables the conversion of lookup fields to KWizCom Cascading LookupApp fields
Filter lookup items by additional columns in the lookup list
Enables creating new item using the "create new item" link
Enables calculated column reference for this type of column
Cross-Browser support (IE, Firefox, Safari and Google Chrome support)