Normally the way I set up a style to reference in multiple places I'll just put it in the deck level script. Then it's in scope for wherever I'm referencing it in code. Depending on what you're doing, it could make more sense for the card level script, it's up to you
As an example, here's something I grabbed from an old project - this is just in the top level deck script, not inside any "on such and such do" events.
ddstyle:() ddstyle.fcolor:colors.black ddstyle.bcolor:colors.white ddstyle.speed:3 ddstyle.border:deck.contraptions.border ddstyle.next:image["%%IMG2AAgABwACAQYAAQEBJAUBAiQGAQIkBgECJAYBAiQFAQEAAQEGAAI="] ddstyle.nextd:20
And then I can just call like dd.open[deck ddstyle] from anywhere.
I'm guessing the grid isn't working for you is because it's passing in like a string containing the text "deck.contraptions.bracket" instead of a reference to the actual bracket contraption.