Would a reasonable approach be that
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When the user saves an instance, either finalised or not, they can mark it as a template.
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This then creates a duplicate of the saved instance but recorded as type "template". Templates would never be submitted to the server. The reason to create a duplicate of the real instance is so that the template can be retained after results are submitted and deleted.
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If the user then clicks on a new button "start template" they will select from the available templates. This will then create a new instance, using a copy of the template instance and open it for editing just as it would if the user had selected a saved instance for editing.