format-ouput.js

const input = {
    page1: {
        group1: [{ url: 'test1' }, { url: 'test2' }],
        group2: [{ url: 'test3' }, { url: 'test4' }],
    },
    page2: {
        group1: [{ url: 'test5' }, { url: 'test6' }],
        group2: [{ url: 'test7' }, { url: 'test8' }],
    },
};


const formatData = input => {
    output = []

    for (const groups of Object.values(input)) {
        for (const urlList of Object.values(groups)) {
            output.push(...urlList);
        }
    }
    return output;
}

console.log(formatData(input))