May I ask why you need this? What you are trying to achieve?
Also to be clear on desired behavior, you want to display two custom fields, for example:
a) Dropdown with job titles.
b) Checklist of systems.
What you want is that different selected values of a) will pre-check automatically values in b)?
We have a "new user setup" in our helpdesk.
When this is selected we have a list of 20+ systems that these users have access to.
Based on a dropdown of job titles, we would like to prefill these systems by using a checkbox for each so that this information can be sent over to our service desk so that they can create the new user.
We are trying to avoid confusion when these new users are to be setup by auto populating the systems that are needed by job title.
Put in an action rule make it so that when a certain job title is chosen the action is "Modify Ticket" Then within the ticket modify choose the options you want for that particular job title.