I didn't see this option in the settings so consider this a feature request, I think it would be useful to configure a show for local and realm time - with some options associated such as indicating positioning (which one appears first, maybe an abbreviation for each one like LT and RT, etc), if they should appear left to right, above and below one another, etc.

Thank you!

No plans for this. But just in case you don't know, you can swap which time the clock displays by left clicking it.