Let's say you always want to have the Line Item Groups of Rental Items and Services on your future projects.
First thing you can do is create a project with those Line Item Groups (one named Rental Items and another named Services, for example) and any services/items that are always included. Then, click "More" in the top right and select "Duplicate Project."
You'll see the option to change all dates on your project.
Now you will be able to edit the date ranges for your new project and add your items.
Need to change all project dates again once duplicated? Click here.