1. Configure Existing Stages:

   • Before creating a new project, make sure you have predefined task stages that you want to reuse. You can set them up in the "Project > Configuration > Stages" menu.

2. Create a New Project:

   • When creating a new project, navigate to "Project > Projects" and click on the "Create" button to start setting up the project.

3. Define Task Stages for the Project:

   • While creating the project, you can set up the task stages that will be used for tasks within this project. Here's how:
     • In the project creation form, under the "Tasks" tab, there's a field called "Tasks Stages". This field allows you to select the task stages that will be available for tasks within this specific project.
     • You can select one or more existing task stages from the dropdown list.

4. Save the Project:

   • Complete the project creation process by filling in other relevant details.
   • Save the project.

5. Use Reused Stages:

   • Now, when you create tasks within this project, the task stages you selected will be available for selection.
   • You won't need to create new stages; you can simply choose from the existing ones you've reused.

A quite good module to configure default stages:
https://apps.odoo.com/apps/modules/16.0/project_task_default_stage/

To optimize stages and to associate stages to projects navigate to Projects> Configuration > Task Stages

This menu is visible only in developer mode