8.5.4. Digitizr
This plugin allows you to digitize a line and have a buffer around it immediately at set width stored in a polygonal layer.
Install plugin
Select a polygon layer and enter edit mode.
Activate the plugin from the toolbar ( button)
To create a line left-click on map on at least two points.
To complete the line right-click on the last point. The line is automatically transformed into a polygon.
In the drop-down plugin menu you can select the style of caps and joins.
In the field to the right of the button you can change the buffer width.