The Object list is located in the right panel and shows a hierarchy of:
You can get a clear idea of the project structure just by looking at the object tree.
You can double-click on a model name in the Object list to rename it. That can be handy when you print multiple parts with generic names exported from CAD software.
The eye icon toggles the printable property. When you disable it, the model will stay on the print bed, but the slicing software will ignore this model during the G-code generation.
Clicking on the Editing icon will open a context menu, which lets you customize the settings for the selected object.