This is trivial on macOS, but I’m not sure how to do it on iOS (specifically, I don’t know how to do it on an iPhone – might be easier with iPad.)
I’ve never run into this issue, however, since I do most of my heavy lifting task management work on my mac. I mostly use iOS for checking things off, some reviews here and there, and quick adding tasks to my inbox to process later on my mac.
I’m sure you could find an OmniAutomation plugin to do this for you. I know there’s one floating around out there that does project templates which might prove useful for you. Here’s a good post about the Automators podcast episode talking about it, here’s a plugin that will import a taskpaper document into your OF database as a project (you can always prefill your template project there), and here’s a great plugin by the amazing @kaitlin with tons of options and things to customize to your heart’s content.
I prefer to just keep a folder of project templates which are on-hold from which I can duplicate to other projects throughout my OF system. But, I primarily am using a macOS device when needing to do that, so I’ve never really needed the plugins.
Best of luck to you!