If you need a copy of the task for your records, you can copy and paste the task.
(Ctrl C, V) This makes an unassigned copy but keeps the original intact.
Assigning multiple users to a task for use with reminders can be done by adding additional Contact List columns to your sheet (one for each user assigned to a task). One workaround that other customers use that will work with resource management is to list the same task on multiple rows and assign each one to a different person.
When setting up your reminders, you will need to set up a separate reminder for each Contact List column. Assigning multiple resources to a task with assignees having different allocation %. You might consider indenting all of the rows underneath a parent header row for the task for organizational purposes. I'm with Chuck Rebew (nice 'fro btw) - I need the ability to assign a single row to a group of people (with or without varying levels of hours worked...).
If you are looking for simple, out of the box, web-based task management, there is already a cool web part available to you that you can use. It has been part of Share Point for a while but in Share Point 2013 (Share Point Online/Office 365) it got a major face-lift and technical improvements, like an ability to display tasks on a timeline. You, of course, can customize it with metadata if you wish.
You'll be able to ask any tech support questions, or chat with the community and help others.Tasks created while viewing a plan, but not placed in a specific spot, will be given diamond icons. If you use a Group by Due date view, you can easily drag a task to a new date.If the task is created while viewing a plan, that task is considered to be a geo-tagged task (one that is specific to that location on the plan), as indicated by the marker pin icon.Tasks that are created while viewing the Tasks tab (not a plan) are designated as non-geo-tagged tasks, and they will have a square icon instead since they signify general work or reminders for the overall project (these tasks are not associated with a specific location).If your organization is using Share Point, there is a pretty robust task management capability built in.