Attention! Mendeley will be removing both public and invite-only groups, user account profiles, and the Funding search feature from the system in December, 2020. You may view more details and announcement of these changes on the Mendeley blog.
If you have public or invite-only groups with citation information (aka metadata) that is important to you, you may want to create a Collection/Folder within you personal library and move the citations from the group into that folder.
If the group collaboration features are important to you, you may choose to create a private group and invite the members to join you there, and the citation (metadata) information can also be moved to the new private group. Note that if your account is part of the UNLV Mendeley Institutional Edition subscription, you have the ability to create many (unlimited) private groups with up to 100 members in each private group.
(Content in this box supplements the Mendeley Collaborate slide deck)
Private groups allow you to share full text copies of papers and other associated files. Note that when you move items within your library between your main library and a private group, you will need to be cautious about annotated pdf files. By default, Mendeley assumes your library copy annotations are private and will only move a "clean" copy of pdf files to the private group. You can export a copy of the pdf with annotations to you harddrive and load it into the private group entry if you wish.