[] Decide where in the code we should fork behavior between the existing template dialog vs. our new design.
- Add a configuration variable, defaulting to disabled.
- Fork behavior superficially, can result in an error dialog or empty dialog.
Notes from story time:
- We are going to group features behind multiple feature flags. The flag in this ticket is for the bulk of changes to the template dialog. The name should say this (e.g. something with "…Sidebar" or "…TemplateDialog").