So from what I can tell you use CSS for everything button related but how do you change the size of it? I can change the font size but I can't figure out how to change the actual size of the check box or a slider. Any help would be appreciated (even just an example).
I just checked the slider and there is an action to 'Set Size' in pixels that appears to work for me, at least the horizontal width does.
Alternatively, you could use the Set CSS action with the settings:
Property = "transform"
Value = "scale(1.5)"
which works on both.