Starred projects appear at the very top of your project sidepanel.
To bring important or frequently used projects at the top of your project list, click the star in the upper right-hand corner of the project.
Hidden projects appear collapsed at the bottom of your project sidepanel.
To hide projects, right-click on the project and select Hide.
Hint: Keep in mind, you can always hide any projects you don't want to work with in bulk by expanding your project sidebar and selecting the projects you wish to hide.