Just had a quick interaction with CS and there is a unique code at the bottom of the get in touch screen that says you may need this when getting in touch.
Now I’m not sure on process but if I had a chat open and they asked me for it, I couldn’t give it to them because the chat box covers the first 3 numbers.
I’ve attached a screenshot and where I’ve scribbled the red box is where the purple CS box appears.
It may never be required in the app because I’ve logged in - I’m assuming it’s mainly for calls but thought I’d flag just in case.
Ps on a separate note, the quick interaction with Sam from CS was quick, friendly and easy.