For the correct work of search helps, you need to specify a data type as TABLE-FIELD.
Important: UI5 uses 1st EXPORTING parameter of search help!
In ui5 search help special RANGE fields are used. In addition to the usual equality, you can use the following characters: >, <, >=, <=, !, …
If the SH is based on the values in the domain, the ListBox is used (instead of the nested SH)