Sounds like the import functionality is not supported when selecting a dual-core microcontroller in the STM32H7 series (and this might apply to other dual-core systems, too). This info is mentioned on page 16 here, "Import from and to dual-core STM32...

Any updates on this? I received the same "multiple context" error when I try to import a project, even when importing a project into the exact same MCU.