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Highlight the entry you want to delete in the list of channel metadata fields.
Then, click the [] button at the top of the list. A confirmation dialog box openswill open.
Confirm with the [Delete] button. A second dialog box openswill open, in which you will be informed , in how many places the metadata field is currently in use.
If you still want to delete it, click [Delete]. The custom channel metadata field is deleted.