The lookup question type has recently received the ability to add chained lookup question to have them function in a dependent fashion. This will allow for the display of records related to the parent question through defined filters. In order for this to be configured first you must create a parent lookup question and designate the lookup filter. Once you have done this you are able to add an additional lookup question on the assessment template and choose to set it as dependent on the parent lookup and set the relationship.

Supporting articles: Lookup filter creation

Chaining Lookup Question to Create Dependent Lookup Question:

Navigate to the ExAM Command Console and select the template that you will be adding the lookup question and dependent lookup question to. You will need to create the parent lookup question first. Once you are on the template you will add the question and input question text as well as select the question type of Lookup, choose the Filter type and select the filter that will determine what records are shown in the lookup list. 

Now that you have a lookup question on the template you can create the dependent lookup question by adding another question to the temple, inputting question text, selecting the lookup question type and indicate that it is dependent. This will allow you to select the parent question, related object, and the reference field. Once you have done this you will click Add question.

You have now successfully configured a parent and a dependent lookup question. The end result will look similar to this when viewed in a public assessment.