> Is it possible to keep (at least a part of) the query 
> string?> E.g. if I mirror ...showthread.php?s=&threadid=5330
> I want to keep '5330'.
> In the userdefined structure options there is only %Q and 
%
> q but no way to add the whole query string or am I 
missing 
> something?
This is badly documented, but you can use %[threadid]
(see httrack --help)

  '%[param]' param variable in query string
  '%[param:before:after:notfound:empty]' advanced variable 
extraction

   param : parameter name
   before : string to prepend if the parameter was found
   after : string to append if the parameter was found
   notfound : string replacement if the parameter could not 
be found
   empty : string replacement if the parameter was empty
   all fields, except the first one (the parameter name), 
can be empty

Example:
%[threadid]
will include the threadid variable

you can also use things like:
%[threadid:_:_:none:none]