Kili Technology allows to draw and edit polylines. To do so, select the object you want to annotate, and click to place a vertex. You can easily cancel the annotation or undo the last vertex positioning. To finish the task, just end the line by clicking on the last point positioned.
It is also always possible to change the class of an annotation with a left click, selecting "Change class", and then select the new class of the object. If the task is multi-classification, this operation will allow you to select all the categories for this annotation : you can delete the previous class but also just add one or more others.
Polyline can be nested (see nested classification)) with all classification tasks, to build refined object classification.