This plugin constructs parallel lines based on a given baseline. It is comparable to an offset line in cad programs / tools, but can construct more than on line.
You have to download the tool and save it into your QGIS Plugin directory. Afterwards restart QGIS and activate in it inside the Manage and Install Plugins dialog (plugins menu). For more details please take a look at qgistutorials.com.
This toolbox was tested with QGIS version 3.0.1.
Select a line feature, click on "Start Construction" and select a side, where to construct the lines. An example of side selection is demonstrated with the following images:
| Construction left of the line | Construction right of the line |
|---|---|
 |
 |
If you click the left mouse button it stores the side, right mouse button resets the plugin.
Finally, click "Construct Units" and a new temporary layer ("Parallel Unit Lines") will be created, in which the new lines will be saved.