Editing vApp templates?

So a newcomer to vCD (a bit too late, evidently). I have spun up an environment to play around with in a test environment. I have everything set up, and I'm now at the point where I want to define / import a template and play with deploying it. Here's what I've tried

1. Imported a VM template in to a vCD organisation vDC catalog, tried to edit it..
2. Created a new vApp template, tried to edit it..

In both cases every setting, except the storage profile on the General tab and the Metadata tab is greyed out. Ideally the template I imported from vSphere would be good-to-go, but changes need making to the configuration.

Is this by design?  If it is, is the correct way to edit vApp templates to

1. deploy a vApp template to a vApp
2. Make the necessary changes to the vApp
3. re-capture the vApp as a vApp template

..or am I missing a trick?