Now that you've added your Collections, you can add and remove projects from it.
First, click the Three-Line Icon to open the left side menu, click HOME and then Collections. From the Collections list, click + Add Projects To Collection. Next, click the search bar, scroll through the list and make your selection(s).
To remove Projects, simply click the X beside them. All changes are automatically saved.
NOTE: Removing a Project from a Collection doesn't delete the Project.
Find out more about Project Status.