One work-around with the way the program works today, if the above example is common across your infrastructure, would be to make a network
Name: Voice Passthrough Trunk
Description: Data vLAN xx, Voice vLAN xx
vLAN: xx - NOTE: I would suggest this be the data vlan since it won't accept multiple numbers.
Network: 0.0.0.0 / Gateway: 0.0.0.0 (only because you have to have something there).
Otherwise you could make interface notes that aren't visible anywhere but the interface. Or Asset Additional Notes which would be visible when viewing the asset.