From the worldcadaccess blog on the new B-thingy version
" The new dimension-style families feature consists of a parent style with one or more child styles. This is a handy way for you to make subtle modifications to just parts of dimension styles. For instance, child styles let you make linear and angular dimensions look different from one another"
This would be a nice feature for Vectorworks to have as well. For example I sometimes need to adjust dimensions in tight spaces where the regular dimension style would not fit, e.g. slightly smaller text and arrows compared to the standard style. Instead of having to create new styles having a child style where the similar parts update together with the parent style if that gets updated (e.g. text style change)