Reference qualifiers are used to filter records of the target table that gets referenced on.
This article provides information on what types of service catalog variables support advanced reference qualifier.
The functionality depends on whether the field show up on the variable form (item_option_new table).
If the field doesn't show up (though present in the Form Layout) when a variable's type is selected, it's understood that this field won't function (even if you try other ways to make it visible).
The following are the types of variables that advanced reference qualifier field functions on:
- Reference (if Use reference qualifier is "Advanced")
- List Collector
- Lookup Multiple Choice
- Lookup Select Box
This indeed is controlled via a UI Policy defined at "item_option_new" table called "Advanced ref qual" that controls the visibility of this field (reference_qual).
Types of service catalog variables (Kingston): https://docs.servicenow.com/bundle/kingston-it-service-management/page/product/service-catalog-management/reference/r_VariableTypes.html
Reference qualifiers (Kingston): https://docs.servicenow.com/bundle/kingston-platform-administration/page/script/server-scripting/concept/c_ReferenceQualifiers.html