Import of registered libraries is rather indirect, available choice limited to already loaded libraries
A user may need to import a registered library such as the standard UML library or the C++ STL library. While the former is already present in the templates, the only option to do that for the latter (unless I missed something) is to create a package import and then modify the "imported element" in the pull-down menu. There are two problematic aspects: (1) it requires two steps to import a library which might not be evident for novice users (2) more importantly, the choice of packages to import is limited to packages that are already loaded. Thus, it is not possible to import the STL library.