I have a vector line and I want to create multiple sequential parallel lines of this line.
How can I do that ?
For example, in AutoCAD you can do many offsets by a determined distance, and I want to do the same in QGIS.
You can use QAD plugin which acts as AutoCAD, and there is an offset tool to that you can use to create parallel line at specified distance. You have to make sure that the tool works only on projected coordinate system not geographic coordinate system, so you need to project your data to before using it, and do not forget to start the editing mode.
This a sample output using offset tool: