Content library signed templates, possible?

Unless I'm missing something I don't think this is possible with content libraries?

The documentation mentions when importing templates that you could add the manifest file from a signed ovf but we I try the import it only asks for the vmdk with no option to add the mf and cert file.

Also I see that the way it stores the template on disk it would break the signing anyway I believe.

It would be nice to loose the no signing warning when deploying but it seems it isn't possible.