I need to put unit behind dual dimensions. I can manually put the "in" behind the top line but cannot put the "mm" behind the second line. Any thoughts?
There is no direct option available by which units can be shown next to dual dimensions.
I would suggest to add text next to the dimension and set the drawing option dual_digits_diff such that to have minimum number of decimal places to the secondary dimension. It will reduce the gap between dimension and text.
The best way is probably to pad the end of the dimension with spaces, either in the suffix or after @D in the dimension properties. Create a note with the units, use the grid properties to align the note with the dimension, and associate the note with the dimension so that if it moves the note moves with it.
You can also use super-scripts and sub-scripts but the units get oriented on with the primary dimension so they appear shifted up.