Formula (Text) field does not work as Available Filter

An alternate solution is to set a Criteria filter for the Formula (Text) field which will provide the default setting for the corresponding filter set in Available Filters tab of the saved search. In this example, we are going to use the formula {message} to pull out data from the Message field of phone call records:  
 
1. Navigate to List > Search > Saved Searches > New. Create a Saved Phone Call Search  
2. In the Criteria tab, add a Formula (Text) field
3. In the popup window, enter "{message}" in the Formula box and set "Formula (Text)" to "contains". In the textfield next to it, enter the character "a". Then, click on Set. This should result to the following line in the Criteria tab:
 
Filter = Formula (Text)
Description = contains a
Formula = {message}

4. In the Results tab, add a Formula (Text) field and set the formula to {message}.  
5. In the Available Filters tab, add the Formula (Text) field as a filter.  
6. Make sure the corresponding "Show in Footer" checkbox is checked.  
7. Set the "Default Text Field Filter" to "contains".  
8. Click on "Save & Run".  
 
Initially, the saved search will show all phone call records where the Message includes the keyword you specify (from the example, all phone calls that include 'a' in the Message). However, notice that the Formula (Text) filter at the bottom of the results list shows the keyword 'a' by default. Try entering another keyword and see if the saved search now runs the filter as expected.  
 
NOTE: Inserting the Formula (Text) field as an available filter in a Saved Search does not provide any option to specify the formula just like how it is when you include the Formula (Text) field in the Results or Criteria tab of the Saved Search's settings. Thus, when entering a keyword in the Formula (Text) filter and running the saved search, no results are returned.