Immediately after installing the plugin, you do not have created timelines

Fill in the following fields in Details tab:

Name - Try to summarize the essence of your timeline. For example: Resource utilization
Project - Select the project / projects on the basis of which your timeline will be built.
Users - you need to select only those people who should be displayed on the timeline, it is better to create different timelines for different teams.
Start, End Fields - Fields that are necessary for the correct display of your tasks on the timeline. These fields should be added to project screens. Important: If you use an unchangeable field as the start date, such as Created, Updated, or other custom fields that are not available for editing, then the task on the timeline cannot be moved using drag and drop. If you cannot change a field in a task, then you cannot change it on the timeline either. Any custom field can be editable, just add it to the edit screen - https://confluence.atlassian.com/adminjiraserver/defining-a-screen-938847288.html
Currently, the only "DATE" type of custom fields is supported. (not datetime)

You must add the dates fields to project screens. So that the timeline can change the dates in the task, while you change their duration on the timeline.

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