If a Filter is visible, that means that the Media Manager and Video Portal displays the filter as an option when searching (if they use that search to gather input from the user.).
Whether a filter is visible or not is defined during creation of the filter:
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It can also be updated in the The Details panel.
For this example, the Media Manager uses a search called DigiZuite_System_Framework_Search:
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If a filter is not visible, it can still be used to filter out results, but the filters' parameters cannot be supplied by anyone other than the client code or Predetermined values.