If you no longer need to use a Registry schema, you can archive it if you have Admin permissions in the Registry. You can also view and unarchive schemas that you've already archived. This article explains:
Archive a Registry schema
To archive a schema:
Click your avatar in the bottom-left corner.
In Feature Settings, select Registry Settings.
Hover over the schema you're archiving and click the archive icon on the right side of the row.
Select the reason for archiving the schema in the Mark as drop-down menu.
View and unarchive a schema
To view and unarchive an archived schema:
In Registry Settings, select the schema archive status in the Filtering by drop-down menu.
Hover over the archived schema. Archived schemas appear dimmed.
Click the unarchive icon on the right side of the row.