In Enterprise Architect 6, an MDG Technology could consist of a multiplicity of UML Profiles, each one representing a toolbox in Enterprise Architect. Each profile could include stereotype definitions alongside redefinitions of standard UML elements. This meant that to define a stereotype in a technology, it had to appear in one of the toolboxes. Enterprise Architect 7 takes a different approach, splitting the task of defining the stereotypes and the task of defining the toolboxes into separate profiles.
In Enterprise Architect 7, an MDG Technology has one, and only one, profile containing all of the stereotypes, so you must define the stereotypes that belong in a technology in a single profile package. You can define them on multiple diagrams if you prefer, as long as the diagram contents all reside in a single package with the «profile» stereotype.
Give the «profile» package a description in the Notes field (eg MDG Technology for BPMN). When all of the stereotypes are defined (make sure that every stereotype extends at least one metaclass) right-click the profile package in the Project Browser and select the Save Package as UML Profile context menu option, then proceed as usual.