Close displayed images with one comand

When I view several images those views are still on the PC screen when I shutdown Opus. How
can I clear those images without shutting each of the down separately.
Thanks for your help.

If you exit Opus, any Opus viewer windows will be closed as well.

That suggests that either the open windows are not the Opus viewer (e.g. the Windows photo viewer is being used instead), or you aren't exiting Opus (e.g. you're just closing a lister or file display, and Opus is configured to remain running in the background).

What to do will depend on which of those is happening.

The Preferences / Viewer / Behavior / Reuse existing viewer window setting may also be of interest. It will prevent multiple Opus viewers from opening by displaying new files in the existing viewer if there is one.