Need to be able to create different "mass measures" that then allow the user to select any number number of beam and shell elements. Each measure will report the total mass of whatever entities have been assigned to it. Importantly, for this usage it would often be important to be able to assign some elements to multiple mass measures.
I build an axisymmetric model of an entire rocket stage which, in practical terms represents a multitude of design elements (propellant tank assemblies, engine support structures, etc). I then run optimizations which provide "first-cut" sizing for shells and beams that provide "least mass" without failing.
There are many common cases where we need to know what the optimized mass of particular "component sets" are. Not having these measures, I must create a spreadsheet, manually enter the optimized shell thickness and beam cross-section dimensions, and slog through providing this mass information to other teams.