When looking at:
@startgantt
[Prototype design] lasts 1 weeks
then [Prototype completed] lasts 4 days
[End Prototype completed] happens at [Prototype completed]'s end
then [Test prototype] lasts 5 days
[End Test prototype] happens at [Test prototype]'s end
[Prototype completed] is deleted
[End Prototype completed] is deleted
@endgantt
which yields:
Is it possible to put the text: End Test prototype left of the last diamond deliverable/milestone?
That would make the Gantt chart a bit less wide, which in some cases can be convenient for readability. I did not find any examples of text left of a deliverable in the examples.