In general, Islamic practice is to keep signs of intimacy in the private without taking it into the public sphere.
But in itself the permissibility of holding hands in public would return to the custom of the country.
If it is from accepted practice that couples hold hands then it would be permissible as long as it is not taken to indecency in front of others.
If it is not from accepted practice that couples hold hands then it would be better to avoid.
[Ibn Abidin, Nashr al-Urf; Ibn Nujaym, Ashbah wa al-Nazair]
And Allah knows best,