After the Lookahead is generated, an Activity can be edited on the below properties:

Instead of editing the activity from the detailed view, you can simply click and drag the whole activity or the end date of the activity.

Editing of start date or duration can delay or advance the activity. If the delay causes deviation from base dates or duration or it happens to be an activity in the critical path, a reason for delay and the responsible party for the reason will be recorded.

Above images show the list of reasons shown for the user to select from when an activity is delayed along with the list to select the responsible party for the delay.
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The activity can as well be deleted if not required anymore in the plan.

However, the progress of an Activity cannot be changed manually by the user after the generation of Lookahead. It will be computed based on the progress of its tasks. Read 4.7 Edit task to know how tasks can be edited.

Activity base dates can also be edited via the detailed view. However, only the users with Project Manager and Planner roles are allowed to edit the base dates of the activities. Watch the video below to learn how to edit the base dates:

Note: