Margin-bottom between buttons not working


i tried to get a specified space between elements (here buttons) with css.
I tried margin and margin-bottom but this isnt affecting the space between the elements.
I dont know what i am doing wrong.
Herre is a little test case for testing:


I think there is an open issue about margins, which ill look at, however, the best way to add spacing to a layout (if it supports it) is probably using “spacing”, eg: