Currently (since branch 3.5) you can select multiple items from the Autofilter dialog. However since Empty is a separate choice on the Autofilter menu, it is impossible to filter data based on a criteria such as (col1 = x OR col1 = empty) or a more complex filter such as (col1 = x OR col1 = empty) AND (col2 = y OR col2 = empty)
This could be simply solved by adding the -Empty- option to the multiple selection dialog (as it is possible in Excel 2007 and newer) instead of (or in addition to) one of the menu items.
Created attachment 98419 [details]
ODS spreadsheet with 3 Autofiltered columns
Please see discussion about this issue in the comments of my answer to
The attached file allows to quickly test the case proposed by user jnnewton
This duplicate bug describes a solution which would be intuitive for the end user, especially those using Microsoft Excel.
*** This bug has been marked as a duplicate of bug 44895 ***
*** This bug has been marked as a duplicate of bug 65505 ***