From BoostSolutions: Build Multi-Level Parent-Child Column Relationships: Build parent-child relationships between a set of columns so that the values in the child list will change automatically according to its parent selection. There is no limitation on the number of cascading levels. Look up Items using Multiple Column Filters: You can use a combination of filter parameters from the source list and the target list to filter items ensuring that only applicable choices are presented in the drop-down list. Create New Lookup Items: Conveniently add new items to the source lookup list with just one click, simply by clicking the "Create new item..." link. The "Create new item..." link name can be changed as per your requirements. Effectively Retrieve Lookup Items: Options to display an empty field when no items match the filter criteria and to display only one instance of duplicated items are available to help make your cascading more efficient. Display Additional Columns: You can add additional columns from the source lookup list to display more details when you look up items. You can also change the order of these additional columns. Allow Multiple Values: Cascaded Lookup allows multiple values as some entries may require multiple entries thus you can add or remove multiple selections to and from a list. Each child field will auto-update as you add or remove a selection from the parent one. Supports Conversion between Lookup Columns: You can convert columns between Cascaded Lookup column, Cross-Site Lookup column and the default SharePoint Lookup column. Cascaded Lookup settings will be retained during the conversion. Manage Column Data in Microsoft Office Applications.
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