MrPAS

Found a workaround. The above solutions did not help me, the slice is still misaligned and therefore the matte adds a border. But it is possible to select a layer filling the whole artboard (a simple rectangle may be added in the background, then "selection from layer" or ctrl+shift+A), then going for the export and instead of choosing the artboard, select "selection area".

Hello, this problem has actually been solved already! If you want to convert a stroke to a form just use the contour tool, stretch the curve out to the sides a bit and you will already see that an outline has been created using the same stroke. Then you only have to press "Bake Appearance" in the context menu and you will have a new curve from the outline. I hope this is what you were expecting from it :)