How to add an element to the Design Tab UI?

Im asking “how” rather than “can we” because I am giving Figma the benefit of the doubt here. When I do figma.currentPage, it seems to only be able to interact with things inside the canvas. I want to interact with the entire app / ui. I want add a button in the design or prototype tabs. How can I do that?

This is impossible.

ah, I gave them too much credit then.

If you want to add a relaunch button that will be shown in the Plugins section of the Design tab, then you can do it like this: