Returning custom attribute combobox values from iPaaS flow to dynamic form

I have a couple of custom attributes to that we've created that I need to be able to populate the values selected back into a combobox in a dynamic form. For example the custom attribute lets you select any combination of (text||value) [Home||1, Office||2, Remote||3, Vacation||4] and stores your selection. The form lets you do a lookup of the service request that holding that information and I want to pull that information back into another combobox on the form.

The problem I'm running into is how do I get the flow to return the right information to set the combobox options to what's selected. I've seen how to return non-table custom attributes but I can't seem to figure out how to get a combobox to get populated based on the attribute.

Edit for clarity: In this example, the form's combobox that I'm trying to pull the information into already has all 4 choices [Home||1, Office||2, Remote||3, Vacation||4] that the custom attribute has. If when someone submitted the form they selected Home and Office when the service request lookup flow is ran on the form it should still have all 4 options in the combobox, but only the Home and Office from the original submission selected.