Assets Imports may be stopped using a UI Button within the Import Progress screen.

(visible when triggering an import manually or navigating to Object Schema>Configure>Process Results>Show progress on a running import)

Once the button is clicked - the progress window is closed, and the process is shutting down in the back-end, and might take some time.

While the process is being shut down, the import cannot be triggered again.

As a Schema Manager / Assets Admin, I would like to see the progression of the Shutdown process in the UI, so I may be aware when can I trigger the import again, as well as be aware of the process being actually shut down...