I've been playing around with the sticker brush and noticed I can import PS brushes into it, which is a really nice feature, but then when I select one of the new brush heads in the presets and adjust its spray parameters and save that preset I want to remove the first imported brush but can't find any way of doing that.

For example if I bring in a "cloud brush" and adjust the way it scatters to get it just right, then I save that as "cloud 01" or something..How can i remove the initial cloud brush?
Also, while on the subject, how do you get the little thumbnail next to the preset? They import with a pic next to their name but when i save a new preset I just get a stock img of the sticker brush.

Same goes for deleting groups in the sticker sheet menu, I can make groups just fine but cant seem to delete them :P

I'm probably just overlooking something really obvious