Swimlane: default size depending on annotations?

I still think it's a bit weird that I always have to adjust the the swimlane size if I have no annotations with duration (and no other lanes). The video is way too small to work with it while there is a lot of black/white space in the swimlane by default.

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I also see the issue that users might not understand where they can find their annotations with duration if you can't see that lane by default or if it's so small, so that you can only see one or two annotations with duration. This might be tricky coding wise, but I'm wondering if the default size of the swimlane could depend on amount of annotations with duration? If there are no annotations with duration the second lane could be quite small, only offering enough space to drop an annotation from the lane above etc.