You can use 3D shapes to make custom objects in your project. Find 'add shape' in the 'add object' button in the toolbar. The button has a plus icon and shows 'add object' on hover.
Change a shape's dimensions
Select a shape and view its properties expanded under the 'objects' tab in the left of the editor. Select 'size' to scale and skew the shape.
Add an image texture to a 3D shape
Add textures to a 3D shape by clicking 'add texture' in its properties. This is great for mimicking UI panels with images exported from Figma or Adobe XD.
Select colour in the object properties to set the hue of the shape once it has a image texture.