jonmac Basically you cant. I suggest raising a support case with Ivanti on this one.
You’d probably need to upgrade though from 2016.4 though as i couldnt ever see them doing a Service Update for a version this old if they did at all.
Maybe someone has worked around by hacking the web source files though so dont lose hope!
Does the field not scroll as you enter the long reference though anyway, making it just a transient bug while you are filled out the query prompts?