Hi! There are different ways you could do this at the moment: one would be to use multiple blocks with a choice UI, and add the different "options" to each block. You could also combine all options into one and use custom CSS or the label names to indicate the grouping.
The only downside is that in all cases, the options would write to the same underlying "accept" key, so you need to allow multiple selection, and you couldn't easily indicate relationships within the grouping (like, only allow one shape and one margin value). I've been thinking about maybe letting th choice UI customise the key it writes to (just like the field_id setting in the text_input interface), so you could have different choice blocks that are either multiple or single choice and store their selection in different properties.