Yeah. It would be difficult to make complex syntax into a perfect UI. However, syntaxs often used by users is limited. Therefore, it may be important to provide a common search pattern. It will improve user experience greatly.
This is one UI example ...
Advanced search: textbox (Existing search box. User input search syntax direcly)
--- OR ---
Search words:
Search words (AND): textbox1 '+' textbox2 '+' textbox3 (Default: Empty)
Excluded words: textbox4 / textbox5 / textbox6 (Default: Empty)
Search conditions:
Search title: checkbox (Default: True)
Search content: checkbox (Default: True)
Search tag: checkbox (Default: False)
Search username: checkbox (Default: False)
Exclude questions less of views : textbox [number] (Default: 1)
Exclude questions less of answers: textbox [number] (Default: 0)
Exclude no best answer: checkbox (Default: False)
Exclude closed questions: checkbox (Default: False)
Exclude hidden questions: checkbox (Default: False) <= Admin only?
Additional script (jQuery):
https://jqueryui.com/tabs/
https://os.alfajango.com/easytabs/