The current workflow to get the TemplateData GUI can be quite convulted:
1. Edit the template page
2. Observe the warning that the data is probably transcluded from Template:Foo/doc
3. Click the link to open Template:Foo/doc
4. Click edit
5. Click "Manage TemplateData"
or
1. Find the TemplateData section on the page
2. Click the section edit link
3. Wait for the editor to load, then press "Manage TemplateData" button that appears late
A better workflow would be to add a small edit button to the output of TempateData that opens the editor on the correct page (e.g. /doc) and launches the TemplateData GUI immediately. This would be similar to the extra edit links wikis sometimes add to template invocations to edit the template itself.
One could also add a "TemplateData" button to the edit tabs.