To exclude entries from search results, or place items in an "Archive" group you can use the "Searchable" setting.
On iOS
- Move the entries into a new group
- Long tap on the group and select Item Properties...
- Under the Searchable heading, tap and select No
On macOS
- Move the entries into a new group
- Right-click or long-press the group and select Properties
- Under the Searchable heading, select No