Can custom smart actions be used in mass update?

Summary:

We have defer options added for individual tasks whereby users can defer tasks by 1 or 2 days, but this must be done on every task which is inconvenient for task templates. Does anyone know of a way to add custom actions such as this to the mass-update selection?

Content (required):

When users use the Task Templates, sometimes tasks are due on Saturdays and Sundays. We have built a custom object-function based smart action on the activity object called Defer 1 Day. Users are able to use this smart action to defer each task by 1 day or 2 days, but this takes a long time to defer every individual task. Instead, we need a way for users to Defer 1 Day (or Defer 2 Days) in bulk. We need the ability to select multiple tasks and defer all of their due dates by 1 or 2 days rather than doing