No, it’s not allowed.
Holding hands isn’t called for in the rubrics so I don’t do it. Neither is imitating the priest by holding out our hands, we’re not supposed to imitate the priest’s posture.
What would be the purpose of holding hands during the Our Father, anyway? It’s certainly not the sign of unity during the Mass because that’s Communion.
It is also not forbidden.
Holding your hands, palms together, fingers interlaced, or fingers pointing out, is also not called for in the rubrics, so by your analogy, it is not allowed either - and I would presume you would not do that either?
The fact that Communion may be the ultimate sign of unity does not mean that there are no other signs of unity.
I have a picture that was taken either in early 1965, or the winter of 1965-1966 in which everyone is holding hands during the Our Father.
That means that holding hands during the Our Father has been going on since at least that time.
Rome has gone through several revisions in the GIRM, and if I recall, the rubrics have been updated in that time period also. Rome has been well aware of the issue for most of that time, and Rome has chosen to respond to holding hands during the Our Father with and absolute, deafening silence. After 48 years of the matter and all the complaints, nothing. In addition to the GIRM, Rome has also seen fit to issue corrections - such as Redemptionis Sacramentum
There is no rule forbidding it, particularly in light of the fact that people have been complaining about the matter to their priests, their bishops, and to Rome. At one point, the USCCB considered requesting permission to hold the hands in the orans position - but that matter never went anywhere.
When he was archbishop of Colorado, Chaput finally published a letter to all about the matter. I don’t consider the archbishop, now Cardinal, to be some sort of flaming liberal; however, he said just what I said - there is no rule on the matter; Rome has seen fit to ignore it, so people are free to either hold hands or not hold hands; neither side has any right to criticise the other, and each is to act in charity. Except he used a few more words than I do.