@中島 祐 ,
Thanks for reaching out to Q&A.
You should be able to change the storage account after creating the Function app. However you will lose the source code if you have deployed it.
When you change the value of the AzureWebJobsStorage setting to a new storage account connections string, the new storage account should have the below containers (azure-webjobs-hosts and azure-webjobs-secrets) created by the function app. After changing the value, you will have to restart the function app for these containers to get created.
This is applicable for function apps running on dedicated app service plan however for apps running on consumption and premium plan, there are additional settings that needs to be added
WEBSITE_CONTENTAZUREFILECONNECTIONSTRING with storage account connection string value and WEBSITE_CONTENTSHARE with storage account fileshare name. Please note that these settings are not applicable for Linux plans.
I hope this helps!
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