Creating a New Group (Folder)
You can check your library for duplicates at any time by clicking Organize tab, then clicking Find Duplicates in the secondary navigation. Any reference identified as a duplicate will have a yellow background. You can quickly check the 'Duplicates' checkbox to check all references with the yellow background to delete those references, move them or copy them to your Quick List.
When using Find Duplicates, EndNote online compares references based on the following fields:
Moving citations to different groups
Sharing Groups with Other User Accounts