Technically you could use the Rule Engine node (MISSING $Var1$ => "YES")
or the Missing value node with individual settings for a specific column:
Or a Column Expression
I still wonder why you have the missing values and still fear that it has to do with the way you constructed your model by (possibly) using University Names in the training. You should be certain that is what you want since it may lead to problems further down the line.
And then we have given you several hints and tried to engage with your case. Of course in a forum no one contributing is entitled to having their remarks taken into account or even being discussed - but in my opinion one could benefit from the debate and 20+ years of experience with machine learning models have taught me to be very careful about my (business) assumptions and what my data really tells me and how I construct my training and test data. I hope you will be happy with your model.