Creation of materials is available from two places in the Asset Editor: the Create Asset button and the Materials category icon (top). If the Materials category is empty, left- or right-clicking the icon prompts you to create a new asset. Otherwise, it selects the category in which case right-click opens the creation menu.
The Asset creation dropdown lists remain active when the Ctrl (Cmd on Mac OS) key is held, allowing the creation of multiple assets in quick succession. The Asset creation dropdown lists can be activated via the Create Asset button or the Asset Category icons.
Material's parameters and options are organized in Basic and Advanced modes. You can switch the mode from the toggle bar under the Preview Swatch or globally from the Configuration rollout of the Settings tab.