Under Overlay - Draw Overlay you can draw and save new overlays on the map. Selecting from the draw tool, you can add objects as points, line or polygons. When drawing a line or polygon, click for each vector and then double-click to finish. You can then modify the shape of the object by selecting modify, to click and move vertices or creating new vertices by clicking on an edge.
As shown below, you can then edit the individual features, naming them, adding attribute data and changing their colour, style and opacity. These can be edited individually or as a group. You can categorise and save the overlay(s) for future use.