Description of the need
I've just implemented hook_theme_registry_alter() in a custom block and checked the registry content to see long list of variables, including for unused layout templates. Disabling them on admin/structure/layouts/settings freed registry from unnecessary content and even-though human eyes might not notice, definitely made things slightly faster.
Proposed solution
I believe Backdrop must be shipped as performant as possible, so I suggest to disable all unused layout templates by default. Users can easily enable them if they need additional templates.
Additionally, we could add a pointer link on pages like admin/structure/layouts/manage/dashboard/configure as shown below:

Recent comments
I think this is the best gift you can give designers—just design, create a new distribution, and get creative with Backdrop.
Add 'recipe' project type to Backdrop
@yorkshirepudding thank you for the additional info on improving discoverability and a handy way to keep a list of projects for reuse.
Why not add a Github star?
It is a good point @izmeez and when I was researching repo discoverability I found that GitHub search does prioritise matches with more stars. This is what I was researching for:...
Why not add a Github star?