How to restrict access to the Filebrowser so that only Channelmember can access

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Hi Community! Following Situation: normally the Access to the Filebrowser is forbidden everywhere on my Server, except one Channel (FileTranferChannel). All Other Channels have the Standard FileTransferPermission, in every Servergroup the permission for Filetransfer are -10. The... How to restrict access to the Filebrowser so that only Channelmember can access