add-designer-extension

Create an Element Extension under a Designer Settings node linked to the foreign designer's GUID, set its type reference to the foreign element's typeId, apply Type Reference Extension Settings with Mode Inherit and Extension Settings, then add options under a [context menu] child.

Use the MCP find_designer_elements tool to search by name in the target application's Module Builder designer, or read the SpecializationTypeId constant from the generated C# model class such as CommandModel. Never hardcode GUIDs from memory.

A Package Extension adds context menu options and new element types to an existing package container, while an Element Extension adds context menu options to an existing element type. Association Extensions target the source or target end of an existing association.

The Designer Settings node is likely missing the Extend Designers link to the foreign designer GUID, or the owning package's Module Settings lacks Reference in Designer. Also verify the context menu options sit under a [context menu] child, not directly on the extension.

No, .designer.settings is regenerated by the Software Factory on every run, so direct edits are overwritten. Always make changes in the Module Builder designer model and regenerate.

Do not use it when defining a brand-new association type from scratch or when extending an element your own module owns. It is only for adding options to elements, packages, or association ends owned by foreign modules.