Hi @逸清 萧 ,
According to my research and testing, the ID is an optional attribute. If provided, specifies the id of the field. It needs to be a unique, randomly generated GUID. You can refer to this article:
https://learn.microsoft.com/en-us/sharepoint/dev/declarative-customization/site-design-json-schema#json-values-1
If you want to apply this script to another site, you can use Add-SPOSiteScript and Add-SPOSiteDesign.
For reference:
https://learn.microsoft.com/en-us/sharepoint/dev/declarative-customization/get-started-create-site-design#add-the-site-script
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