Now you can have a manually scheduled task placed anywhere in your plan, and Project Plan won't change it. This new improvement gives you greater compatibility with all plans created in Microsoft Project.
Manual tasks are tasks with task mode manually scheduled. They should be used when you want to explicitly set a task's start and finish dates and not allow it to be changed automatically by the scheduler based on changes to other tasks.
When a task is in manually scheduled mode, the Start, Finish, and Duration columns can be blank or include text values in addition to recognizable dates.
Manual tasks and interaction with other scheduling fields:
Duration, Start and Finish date can be text, number or dates -this values not used in scheduling process.
Constraints - can be used but this value will be ignored
Resources - can be assigned to tasks, this values not used in scheduling process.
Dependencies -can be used but this value will be ignored
Project and resource calendars - will be ignored
The Task Mode field indicates whether a task is scheduled manually or automatically, which gives you the option of deciding how much control you want over task scheduling in a project. By default, tasks are set as auto scheduled, with a start date, finish date, and duration calculated based on inserted fields values.
The Task Mode field is not included by default use Insert column options to insert and display Task Mode column in views like Gant Chart, Tracking Gant or Task Sheet view. Task Mode column displays an icon indicating whether a task, a manually scheduled task, or an automatically scheduled task.
To change the task mode, click in the field. In the list that appears, click Manually Scheduled or Auto Scheduled. You can also select specific tasks, then on the Task Information General tab, in the Schedule Mode group, select Manually Schedule or Auto Schedule.
If you want to use in plan all tasks manually before you start plan set manually schedule mode from Options dialog--> Scheduled tab, all new inserted task will be in Manually Schedule mode: