Hi @YaoZong Wang (汪耀宗),
It's possible that colleague B's Office application is not configured to trust the shared folder as a catalog for add-ins. Follow the instructions in the "Specify the shared folder as a trusted catalog" section of the Microsoft documentation to configure the trust manually or with a registry script. Once the shared folder is added as a trusted catalog, colleague B should be able to see the 'SHARED FOLDER' in 'My Add-ins'.
Reference:
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