This setting is not necessary nor recommended unless you are using a filter that determines filter names to be sent dynamically, rather than using a fixed one you entered for the filter, such as catch-all Page Request / URL Filters.
Connected Web Parts may or may not inform the FilterZen Filter Web Part about the names of filterable columns. This information is not always necessarily complete. For example, when you connect to a List View Web Part with three visible List Columns, then it will notify the FilterZen Filter Web Part about these three filterable Columns — they become 'known filter names'. However, you can still validly use any other Column Name present in the List but not the List View, and filtering will still work as expected.
If this setting is activated, filter values will never be sent if the corresponding filter name is not in the list of 'known' filter names. This setting may work against you because the list of 'known' filter names is not always exhaustive. It may be useful, however, to build a single "catch-all" Page Request Filter that takes all URL parameters as filter name-value-pairs, but sends only those that are known, visibly filterable Columns.
By ticking the Override Web Part and filter settings from URL parameters checkbox, every filter setting or Web Part setting is overridden by the appropriate URL (query string) parameter value, if it exists. See the possible parameter names and values in the reference chapter.
All filter types (except Page Column Filters and Page Request / URL Filters) support the so-called interactive mode which you enable by ticking the Allow users to enter / pick a value check box. If interactive mode is enabled for at least one of your filters, the FilterZen Filter Web Part renders an interactive filtering user control appropriate for the filter type (date pickers for Date Filters, drop-down lists for Choice Filters, User Filters, List Lookup Filters, SQL Data Filters and BDC Filters, and text boxes for Text Filters into the Web Part Page, allowing your page visitors to change the filtering on-the-fly. The appearance of this Web Part output can be customized via CSS.
If interactive mode is enabled for at least one of your filters, the following additional Web Part settings are available:
Interactively input filter values are applied during the next server post-back, whether the above option is active or not, and regardless of how exactly the post-back was initiated. You can force such a server post-back by calling the roxRefreshFilters(filterWebPartID) JavaScript method. Just below the Web Part settings described above, there is also a text area for you to enter additional HTML mark-up code to be rendered into the Web Part area, depending on your choice either prepended or appended to the interactive filtering user controls.
Want to offer interactive filtering user controls for all your columns without having to set up all these filters manually?
You can have the FilterZen Filter Web Part generate the appropriate interactive filtering user controls for you automatically, on-the-fly during each Web Part rendering for all available 'known' filter names. This time-saving feauture generates drop-down filtering lists for choice and lookup Columns (appropriately pre-populated and pre-filtered), date pickers for date Columns and text boxes for all other Columns. To activate dynamically generated temporary interactive filters, from the drop-down list labelled dynamically generated temporary enabled interactive filters for all 'known' filter names if possible, select Prepend or Append.
When a filter does not seem to work as expected, it can be helpful to find out which filters exactly the FilterZen Filter Web Part constructs and sends, given its current settings. The FilterZen Filter Web Part will render just that information whenever the page is in edit mode, so on the page that does not result in the filter you want, select Edit Page from the Site Actions menu and you will see all filters produced from the current setup. Also shown are all the filter values that were not sent, if any, and the reason. Unless the FilterZen Filter Web Part is minimized or hidden, its Debug Mode output looks like this: