Edited this post after I discovered how to do the two main things I asked about.

I had asked about having a task-to-template option, then discovered there was one. I hadn't seen it because I was looking for it under the 3 dots within the task, but I saw it when I right-clicked on a task.

Discovering that helped me figure out how to duplicate a template. The right click option to duplicate a template doesn't seem to work for me. But now I know I can drag a template to the day's task list, edit it there as needed, and then task-to-template to make the duplication.

One suggestion remains: ideally I'd like to be able to re-order the template list, so that I can group the similar templates with each other, even if they were created at different times.