At least in v1.14.0 and with the text input widget, msg.ui_update.label or msg.ui_control.label have no effect.
(I might be doing something wrong, I only ever used {{label}} in dashboard v1)
Is this available yet? If so how can I install it? Is there any end user documentation?
That shows our progress on this in the tasklist of the issue description.
We had a little hiccup on some architecture changes which put a pause on it, will be continuing this week, and they should be covered in the (to be released) 1.15.0
Our documentation also gets updated with the relevant features too, so will detail when the dynamic properties available.