You can easily set a components height or width to "Automatic" or "Fill Parent" in the Designer, but there is no obvious way to do this with blocks.

All you need to know is this:

Automatic = -1

Fill Parent = -2

Just use those values with a component's Height or Width block to get those settings 

Also, resetting default colours for buttons, labels, textboxes: 

set backgroundColour to 0 or 1