MisterTicot Hey! That'd be awesome. Right now it's a bit more roundabout than simply adding the data entry to your account on the network since Nucleo doesn't have a listener server-side yet (implementing Stellar Notifier is on my todo list).
The data entry value is your Nucleo profile user.id signed by the Nucleo server key so you'd have to extract it manually from the browser console input[name=signed_user].value, submit the tx to the Stellar network (see below for details), then POST data { public_key: YOUR_PUBLIC_KEY } to https://nucleo.fi/account/create/.
Alternatively, I could implement cosmic links to make things easier. There's a JS SDK right?
transaction = new StellarSdk.TransactionBuilder(sourceAccount)
.addOperation(StellarSdk.Operation.manageData({
'name': 'nucleo_signed_user',
'value': $('addStellarModalForm')[0].elements["signed_user"].value,
}))
.addMemo(StellarSdk.Memo.text('Nucleo Account Verification'))
.build();
