I want to transfer a selection from a google sheet document to a google docs document via my node.js backend service. I was hoping that the google docs API supports this feature, but I can't find the exact steps needed.
To visualize what I want to do, I have taken a simple screen capture in the web UI, that shows exactly what needs to happen - just not handheld, but automated in my backend service:

It is my understanding that the google web apps almost uses the exact same API as is exposed to developers, so I was hoping that someone here can tell me what exact requests are made for this to happen.
This question is somewhat similar: Copy selection from Google Sheets into a Google Doc (using REST API?) but it 4+ years old, and haven't gotten much attention, and a lot have happened to the APIs in the meantime. Furthermore I am not interested in using app scripts, which the answer suggests doing.