1. First you need to create a Kit that will act like a folder for your future templates. Click the New Story button and then the Add kit one:

Alternatively, you can click the Change Template option below the scene and the Add Kit:

2. Give your kit a name

3. You can now create scene templates, one at a time in this kit. To do so, go back to your story Click the 3 dots menu on top of the scene you want to save as template. 

4. Give your template a name and place it under your newly created kit. Optionally, you can add a content category to it.

Note:

You need to create separate templates for each scene type (cover, standard, quiz, poll) - and they will show up once you switch the category at the top (ex: add new scene > quiz scene - will show you only the quiz templates you have previously created).