• Create new empty project
• Drag Rectangle from item library to the scene
• Right click on the added rectangle and select "Create component"

--> A new component is created from the rectangle, but UI doesn't seem to be aware of it in any way:

• Nothing is added to item library (My components)
• Navigator still shows Rectangle icon instead of component icon
• Property view still shows Rectangle as the type for the node

If you close and reopen QDS and the project, new type works correctly.

There is also the following error message on application output when you close QDS, it might be related:
C:\dev\qt\DesignStudio\qtc_PS2\qtcreator\src\libs\sqlite\sqlitebasestatement.h:write:210: Sqlite::PrimaryKeyConstraintPreventsModification