I do not know whether i miss something here, but as far as I understand it is not possible to search in advanced search for a search term in any field. This is very inconvenient, because I can only save searches from advanced search, not from simple search. It would thus wish an option not to set a specific field, but to search in any field also in advanced search.

At the moment, if I want to save a search for all entries that contain "smith" somewhere, I have to do basic search for smith, then tag the results with "smith", then do an advanced search for tag="smith" and only then can I save the search.
This is inconvenient, specifically because every related to tagging takes so looong.

Second, I would wish that there would be the option to search not only for specific contens of fields, but also for empty fields or not empty fields.