Updating flutter widget tree at runtime

Question

I am doing a research for a project I will be starting soon. Basically, the app let's the user create a design by dragging and dropping some widgets like Text, Stack, Container etc. Kind of like a visual app builder. How can such a feature be implemented. My approach would be updating and saving the widget tree at runtime. But I don't know possible it is to access and modify the widget tree at runtime. Please I will really appreciate your suggestions on how it can be done, a better approach or projects/source code I can look at.