Cloning for Function Apps is not supported. An example as to why this is for apps in the consumption plan is that these will not have a dedicated file system to store the file content. Additionally, this feature for Web Apps depends on having a storage account for storing app life cycle components.
As such, the current recommendation to accomplish this would be to use the export template feature in Portal and then use this to create a similar function.
Once the Function is deployed using this template, the final step is to add the storage app settings as mentioned here- https://learn.microsoft.com/en-us/azure/azure-functions/functions-recover-storage-account#required-application-settings
Although we do not offer this feature at the moment, if you would like to see it in the future then please upvote the ask on our UserVoice site- clone azure function – Customer Feedback for ACE Community Tooling