To see all tasks, documents, and milestones across all active transactions navigate to the Calendar view. Dy default you will see the items across all transactions where you are set up as a transaction owner. If you have access to the transactions assigned to other users you can see what they need to do by using appropriate filters. By selecting the "All transactions" option in the dropdown, you will be able to see everyone's tasks across all transactions you have access to.
All items in the calendar will be shown in the order, where everything passed is at the top, followed by anything due today, this week, next week, down to the items that do not have a due date.
Any of the tasks that do not require a document can be checked off directly from the Calendar and they will mark themself as complete on the transaction. If the document is required, it can be uploaded to the calendar as well and will disappear from the list as it will be marked as complete on the transaction.