I don't think you can pre-create these - the only way I can see would be to create a blocking task which adds the appropriate metadata before allowing the operation to proceed. See here for reference on blocking tasks in vCloud Director:

Configuring Blocking Tasks and Notifications

If all you want to do is ensure that metadata is created if not already present, you may be able to use something like my PowerShell module ( https://kiwicloud.ninja/2016/02/working-with-vcloud-metadata-in-powercli-part-1/ and https://kiwicloud.ninja/2016/03/working-with-vcloud-metadata-in-powercli-part-2/ ) on a scheduled basis to identify objects which don't have a particular key/value set and create these entries.

I've also written some scripting internally to synchronise vCloud metadata with vCenter tags - we needed to do this as we have some 3rd party software which updates vSphere tags but doesn't understand vCD metadata, I should probably write a followup article on this when I get some time as may be useful to others...

Regards, Jon