I guess you need to create a Custom Search Properties rule instance.
If you have introduced a new application specific property and you want that to be included in the elastic search then you need to create a new Custom Search Properties instance in the applies to class of that property and include all the such custom properties there.
Also make sure in the Configure → System → Settings → Search → Dedicated tab your custom search properties are successfully indexed.
@MaxonL16591286 you need to add the property to custom search properties rule instance and rebuild the work class. Please check the below url for reference.