Interesting question, and I like @Springer’s answer. However I always act to reduce the apparent complexity in my filters so my best filters do not appear complex M.I.S.S “Make it simple sweetheart” is much better than the KISS principal.
A real boon to this simplification process is now available with functions and custom operators. This allows compound filters to be written in an easy to read way. I consistently try to generalise functions for reuse and move them into global functions and procedures. Then subsequent filters are built on top of those utility functions.
I have also found it quite easy to present ChatGPT with the JavaScript found in a core filteroperator module and ask it to “write one” for me. It is amazing how reducing filters to simpler meaningful ones can make complex filter authorship much easier. We have discussed this in the past and its about reducing the cognitive load when composing solutions.
Eg; Consider balance.fields[creditfieldname],[debitfieldname] to subtract debitfieldname from creditfieldname for all titles given to the filter and that have the fields.
For me the most complex filters are the ones I do not yet understand. See recursive functions in this conversation by @stobot and @saqimtiaz