Got it
If the data is all going to be saved/stored/queried in the app, the data structure should first reflect the types of content which will be inputted and saved by Users.
For example, Civilian, License Plate, Ticket, Vehicle, and Warrant will probably need to be their own data type, with the fields needed for each. Then each of those custom data types will have fields within them, that you can then use in the search box element. Currently you have the type of content for each field as type ‘List of Civilian Registrations’, which is not a text field and won’t display as an option for the search box element.
If you create a new type for each of those fields, this should work. For example, you could have a new data type such as ‘Civilian’. Within that type, there could be fields such as ‘First Name’ (type: text, list: no) and ‘Last Name’ (type: text, list: no).
Each Civilian will probably have one or more License plates, so you can create another custom data type called License Plate.
Within that type, you can ‘link’ a Civilian to it by creating a field within License Plate called ‘Civilian’ (type: Civilian’, list: no). Then add other fields to the License Plate data type, that are needed, such as ‘Number’ (type: number, list: no). To make querying easier, you could also add a field to the Civilian data type, to store their list of License Plates, called ‘License Plates’ (type: License Plate, list: yes).
I would focus on creating and saving the data in the way you need to first, and then you can use the searchbox to query the data. 