Sounds like the MVC design pattern, which should allow for the logic code to be shared between all platforms and yet the UI to be native for each one. It was hard to wrap my head around coming from Xojo, where I simply double click a button and enter code.
I believe to do x-plat with Xojo, you need to adopt this or a similar model, if you use the Xojo way, it becomes much harder to maintain x-plat apps.
It’s no wonder really as to why more and more companies are simply going for Electron. Design once, use a web based UI and screw native.