The Tool Bar is used to select the current editing tool. The current tool determines what you can interactively select and edit within the 3D Edit Window.
Refer to the Tools page for documentation of all RoadRunner tools.
Click the desired tool button on the Tool Bar.
Certain actions automatically change the active tool. For example, dragging certain types of assets from the Library Browser into the scene adds that asset to the scene and automatically switch to an appropriate tool for that asset.