We have a number of projects that were created with extra or unused tasks. As a result many timesheet users have timesheets that have lines and lines of tasks that will never need to have time entered against. How does a timesheet user delete tasks from their timesheet? 

Thanks.

 Only the manager(s) of a project where those tasks came from has the authority to delete tasks.  Fundamental rule of Daptiv.  If your user happens to be a manager and they're in the timesheet - they click the task name and Actions>Delete.  Otherwise the manager needs to go into the Project>Tasks or Tasks global tab and delete tasks (which will remove them from respective user timesheets. 

 Can someone delete tasks just from their timesheet view but leave them intact on the schedule?

The issue seems to be that we use Projet Transit and MS Project for most of our projects and PMs are reluctant to delete tasks from their MS Project file because we have had enormous problems with tasks being deleted that had actual approved time attached to them. 

A timesheet only user can have loads of tasks on their timesheet that they'll never actually put any time against because the tasks didn't actually correctly detail the work that was done and it creates a cluttered timesheet. How does one clean this up?

The Timesheet is just another interface to the task that was created from the project so deleting a task in one area deletes it from all areas.

 I would have the manager create a Task Tab view that shows the Task Name grouped by project, lists only overdue tasks (and/or incomplete tasks) and include a filter where Actual work = 0, include Create Date in the view .  Anything that shows up on that view that is old, delete it.

 What you have left are tasks that have work applied to them.  In another view take any old tasks with Actual Work and just select all>mark as complete.  This will clean them out but save them.  I think you could also just put the tasks on hold if you don't want to mark them as complete, any task on hold shouldn't show up on the timesheet if I recall.

Also, there will be a new alert about deleting tasks via PT where if they have work applied you will be prompted to take an action.