To edit numerous projects and change their project assignee or due date, use the Bulk Edit toggle, located in the top right corner of the Projects page.
In order to edit numerous projects at once and change their project assignee or due date, follow these steps:
Apply any filters to narrow down your projects to a specific project name or owner, if applicable.
Toggle the Bulk Edit on.
Select all projects you want to edit by clicking the checkboxes to the left of the project name. As you start to select projects, a drawer will open on the right side of the screen.
Once you've selected the projects you intend to edit, make the changes to the project assignee or due date and click the blue Update project(s) button in the bottom right corner of the screen.