In case if you are creating a project from the Sales order Then,

You can create a service product and under the sales tab, "Create a task in sales order's project" and it will allow you to select a template project.

When you confirm the sales order, It will create a new project and task from the template project you have selected on the Product.

Hope this will help you.

My advice: 

- Create a project and its tasks. Name it, for example, "Project Template".  
- Edit the task stages so this project can use them. 
- Configure assignees, planed hours, etc. 
- Save it and don't fill any worksheets on it. 

You can duplicate it when needed and change the name and whatever you want. 

You can also configure a Service product (general information tab) with "create on order --> Project" and put your template on the field "Project Template"

Hello, I am using Odoo Online V17; how do I achieve the same?? Thank so much

Hi, is there a way to include the number of days per task on a project template, and given this once I start a new project with this project template and select the start date of the project, for the system to automatically calculate the actual dates start and end dates for all the sub sequent activities? 

https://odoo-community.org/shop/product/project-templates-4764?version=14

Hope this will help you.