Overview & background
You can update the task attributes for multiple tasks at once from the Kanban Board through the 'Batch Edit' feature.
Note: This does not mean that you can leave task comments in multiple tasks at once. You can only update the task attributes, such as title, priority, start/end date, etc.
How to batch edit task attributes
Note: Batch editing is available on the web version only
Go to the tasks view
Hover your cursor over each desired task and click the checkbox that appears.
Once you have selected the tasks you want, click on the 'Actions' button at the top of the Tasks page (which will turn red once you've selected multiple tasks) and you can then edit those tasks in a batch action.
Keyboard shortcut: As a shortcut, you can click on one task, hold down the 'shift' key on your keyboard and then click on any task above or below the first task you clicked on to select multiple tasks in a row.
Keyboard shortcut: Another keyboard command you can use to select multiple tasks is to hold down the Mac 'Command key' or 'Windows key' and then to click on each task you want to select and the tasks selected will be included in the multiple tasks selected:
When you click on the "Actions" button, you then select 'Batch edit' and you will see the pop-up window below:
Note: Project followers or members may not see all of the Statuses if the project uses Custom Task Status. This is because custom statuses may be associated with specific permissions (Admins Only, Admins & Members, and All users). Read more about custom task statuses in this article.
Note: If you see a red "Conflict" for an attribute in this "Edit" screen, that means that all of the selected tasks have different attributes currently set (for example, the tasks might all currently have different assignees or titles).
Tip: Editing those conflicting attributes will then affect all of the selected tasks and give all of them the same assignee or title.
Video Tutorial on Creating Tasks