nested unique flat in javascript

Is there some super new ES JavaScript magic that can achieve this ? (I can write a function to achieve this, was just wondering if any new ES202* technique exists )

let arr = [
    ['cb', ''],
    ['cb', '34'],
    ['cb', '35'],
    ['rb', '1']
];

/*
Required Output : 
[['cb', ['34', '35']], ['rb', '1']]
*/

console.log([...new Set(arr.flat(1))])