The bulk editor currently does not support adjusting object policies, so you can't use it to (for example) change the visibility of a large number of tasks.
In the meantime, a possible workaround is that all modern *.edit API methods do support policy editing, so you may be able to use the API, rather than the bulk editor, to make sweeping policy changes.
The bulk editor doesn't support setting custom date field values. This is also a control problem, but this can be supported with a simple variation of the control (just a text field) until the fancy version (with the calendar picker) gets built.
- See PHI2070.
The action menu in the bulk editor has no option for "Change Policy" / "Change Visibility" / etc