The ability to select multiple assemblies at the same time would be extremely valuable, instead of having to duplicate them individually. For example, in concrete estimating, I may want to select a footing assembly, a wall assembly, and an anchor bolt assembly all at once, then go around the drawings and have the software pull the linear footage (LF) for each simultaneously.
My previous estimating software, Maxwell Quest (which later became Viewpoint Pro Contractor), had this feature, and it was incredibly useful. Unfortunately, that platform is no longer available, but this functionality made the takeoff process much more efficient and streamlined.