Customized stereotypes should be contained in one or more profiles. The stereotypes within each profile use the profile name as the namespace. You then add the profiles into an MDG Technology.
Create one or more packages with the «profile» stereotype, each package name being the namespace. Within each package create profile diagrams defining all the stereotypes in the namespace. You can use multiple diagrams to do this, but do not use nested packages.
Give the «profile» package a description in the Notes field, such as MDG Technology for BPMN. When all of the stereotypes are defined (make sure that every stereotype extends at least one Metaclass) right-click on the profile package in the Project Browser and select the Save Package as UML Profile context menu option, then proceed as usual.
To define an MDG technology's Toolbox pages, you create a separate profile.