Until now there was no way to change a stroke's cap type without twirling down and changing the strokes manually, for every group, for every stroke, on every single layer.
Now you can change stroke cap and join types on selected layers, selected groups and individual strokes or across the whole comp (by not selecting anything).
ButtCapper is focused on keeping you moving. By holding ALT/OPT on the keyboard you also change the Stroke Join type.
Because screen real estate is so precious in After Effects, ButtCapper exists in two forms: as a stand alone panel and as individual headless scripts to be run from FT-toolbar.
Battle Axe is a small design and animation studio that also builds tools for people to use in their own projects.