In the ArcGIS Online Map Viewer, when you add content, you can search in My Content, My Organization, Living Atlas, or ArcGIS Online. From ArcGIS Pro, you search My Content, All Portal (My Org), and Living Atlas.
Is there a way to search for ArcGIS Online content that is not in your organization and is not included in the Living Atlas? The only workaround I have is to search for it in ArcGIS Online, find the item page, copy the URL, and then Add Data from Path in Pro.