Linux

Just having something that shows the field options and formats it correctly would be fantastic. Tooltips and all that could be added later to lower the bar of entry for new users.

Even if the new service is "just" a text field for code + the name of the service. If it saves it in the right location for you its useful. Not having to fiddle with that stuff as an end user is nice.

I would absolutely use it. In fact creating and editing services would be the primary selling point IMO. It doesn't need to be much "easier" than doing it in the terminal or file explorer, to me the primary benefit would just be the ease of use of creating, loading, and starting a new service all in one place.

I think a generic template would be great.

You could turn the whole thing into a giant GUI settings screen, allowing navigation to an exectuable, after which you could provide some of the most typical options as sliders, number fields, switches, or whatever is suitable. But that would be a large amount of work, and I'm not sure it would simplify things much.

The starting point should just be a text field, but with a link to the service file docs for help/reference.