Double clicking on one of the ribbon bar labels (Data, Displays, Components etc) hides the ribbon bar to give you more screen space. Single left clicking on one of the collapsed headers allows you to temporarily access the ribbon bar. Double clicking on one of the labels forces the ribbon bar to stay pinned to the top again.
F12 collapses the header of each display item as well as the ribbon bar to give you more screen space
You can hide the project tree by hovering over the separator bar until the cursor changes and left clicking. You often don't need the Project Tree showing while using the software.