Today is one of those days where I've got tons of ideas on how to implement the next part of my app's functionality. Then I remember I'm using Swift. Forehead, meet wall, again, and again, and again....

I insist you to watch "the principles of clean architecture"
https://youtu.be/o_TH-Y78tt4

If you will refactor your code following this instructions, you will be able to complete your feature, without the need of the GUI.

And!
If you want to use another rendering engine with the same app-code, it needs just a few presenters and templates for the other templating-engine.