Hi
Yes you can see the variable live and in-play. There were no in-play races to show this so I used an in-play Correct Score market.
The trigger above is running and updating a user variable called "laybook".
I opened the User Variables window as shown with the arrow and popped in the variable name. You can see it shows the lay book %
Another way to display it is to switch to Engineer Mode screen and put the variable name in one of the cells. It shows the market lay book % next to each selection.
By the way, you can see the last two selections do not have a lay price, and the figure displayed is the lay book % of all selections with a lay price.