The last thing you want to see, in your projects, are lots of old tasks which have been completed. It's important that you clear out the dead wood, and mark all your completed tasks as 'done' so they disappear from view. Not only does this keep your task management system better organized, it'll also give you a wonderful sense of progress, and positive energy.
Crossing Tasks Off Your List
To mark a task as complete, simply right-click on the task in question and then, from the right-click menu, select the 'mark as done' option as shown below:
Fig 1: The 'Mark as Done' Menu Option:
Once you click the 'mark as done' menu option, a confirmation window (shown below) will appear. Simply click the 'OK' button to confirm the task is complete. Clicking cancel will cancel the process, and leave the task as incomplete.
Fig 2: The 'Mark as Done' Confirmation Popup:
Note: Your completed tasks will disappear from view, but can be viewed using the '@completed' context filter. More information on system contexts can be found here.