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BUT: Only select filters you can make dependent on other select filters! Hidden filters can NOT be used!
e.g. for your user report you only want to be able select users from subcontainers ou=users,o=data. You define a filter on attribute parent as described above in querystring definition. Subsequent filters like lastname (sn) and givenName you want to make dependend on what you select in the parent filter. You only want to show lastnames and givenNames of users in the container you have selected in the parent filter. In that case you have to make the filters on attribute sn and givenName dependent on the filter defined for the attribute parent.
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Hidden filters do not show up in the filter selection when generating the report. So hidden filters have NO EFFECT on select filters even if you make select filters dependend dependent on hidden filters!
Hidden filters are used mostly if users want to generate a report but do not want to or should not make further filtering. So all filtering for the report is predefined and the report will be generated without further interaction for filtering.
If you nevertheless define select filters on a report that has hidden filter(s), you have to add your hiddenfilter(s) to each select filter in the querystring expression. Otherwise in your select filter(s), values will appear from objects, that will not show up in the report (hidden filters have NO EFFECT on select filters!). This is because the hidden filter(s) are applied after the select filters.