Im trying to talk myself into getting a MK 4
With my Mk3 I quite often "hand brake on into Neutral" when stuck in traffic mainly to keep my right knee happy.
How good is this "Brake Hold" thingy
I’m old school like you, I was taught to use the hand (parking) brake and I continue to do that, but I’m not sure I understand the problem you’re trying to solve here. Your profile says your Mk3 is a CVT, so you’re already well used to having just two pedals, both of which need your right leg & knee. I presume you then apply the parking brake so can take your right foot off the brake pedal (you don’t keep your foot on the pedal, do you??). The Mk4 is no different: you brake to a stop and then either apply the parking brake (which is a simple electrical switch rather than the big lever) or let the brake hold thingy hold you in position. So I can’t see how the Mk4 controls will be significantly different for your right knee.
Personally, as the driver behind you in the traffic queue, I’m not a big fan of brake hold because of the light issue. It’s hardly difficult to avoid it by using the parking brake, but so many drivers these days simply can’t be bothered. What does that say about how attentive and considerate they are?