Streamline templates: how to use !include to put them in a more convenient folder

I've become a big fan of streamline templates. I have eight of them; the best combines Nerwyn's universal remote control and a lot of additional buttons and sound control for each TV in the house. Overall that is 474 lines of streamline templates.

I've been trying to improve the organization of my main dashboard, of which there are three versions (mine, wife, tablet). As part of simplification, I switched to YAML mode, and one of the benefits is the ability to put

streamline_templates:
  !include_dir_merge_named /config/dashboards/streamline/

in configuration.yaml, so that my templates are conveniently located in the same folder as my dashboards. That hasn't worked.

First, I have all the templates in a single file

/config/www/community/streamline-card/streamline_templates.yaml

and it works; I would like to move that file to /config/dashboards/streamline/ and have it work. So far it doesn't. So do I need to include the !include statement in the space above views in my dashboards, along with button_card_templates, in which case I would presumably lose the /config/dashboards preface?

Second, the github description suggests that you must have a separate file for each template if you are going this route -- is that true?

It would be helpful if someone could share working code for including templates in an alternate location than the default.

Thank you.