When the density of a part is not defined and the mass calculation is run, it pops up a dialog asking for the density. This needs to allow material selection as an option.
When it is run on an assembly full of parts with undefined density, it still asks for the density for one part. Enter it, then it asks for another part. Enter it, then it asks for another part. Etc. There is no chance to cancel, and no chance to select materials.
The density selection dialog needs to be replaced with the opportunity to select materials, define all densities at once in an easy table format with tools for easily applying the same value to multiple parts, AND the whole process needs to have a Cancellation button to end the attempted calculation.