We actually have a workaround for this question. If you leave the workspace, you will automatically unfollow all items in the apps. So the workaround will be to:
- Leave the workspace where you want to unfollow all items from all
- Get invited back into workspace by a colleague
- Manually follow the items you will like to follow.
Another option would be to use an "admin" account to do the import and general update work to avoid having your personal user follow too many items.
Final option would be to use this beta feature (not officially supported yet) to see all the workspaces and apps you are following and do a big bulk "unfollow": https://podio.com/home#subscriptions
//Sara - Podio