A really quick project because - We can set the pen opacity now (transparency, or how see through the pen lines are). It remains to be seen whether this feature will stay working as it is because it is difficult to actually use, and very difficult to then do anything more than transparent dots or lines ;) What we really need in my opinion is filled polygons, then transparency would be very useful! (Although see @TheLogFather for clever projects which are bridging the gap to make even that possible)
