Allow Multiple Contacts Per Cell

Thanks for the question. Please take a look at the left side of the Column Properties screen you provided, which will tell you why the column type is currently locked down. Your screenshot shows the top of the message: "The column type cannot be changed because it is:" but I can't see the rest of the message in the screenshot. The rest of the message will explain what you need to do to uncheck the box. For example, if the column is being used in Conditional Formatting or Resource Management, you'll want to temporarily remove it from that feature to allow the change.

Best regards,

Daniel