Ability to Sort Dimensions in Forms

We have a form that we use to plan our staffing compensation for future budget years. It is essentially a roster and the first columns are all dimensions that our users want to be able to sort off of (position ID, Employee name, Fund, Function, Project). Currently, it only looks like we can sort by position ID. We can also sort by Home Dept, Staff Job Code (see attached image) and other column headers. We are unable to sort by the other headers.

Does anybody know where there is an explanation of how the sort/filter functionality works for dimensions in the web app? We are able to sort/filter using the flex form in smart view, but cannot find similar functionality on the web.