Explorative and live development environments flourish when they can impose restrictions. Forcing a specific programming language or framework, the environment can better enhance the experience of editing code with immediate feedback or direct manipulation. 
Lively Kernel's user interface (UI) framework Morphic provides such a development experience when working with graphical objects in direct way giving immediate feedback during development. 
Our new development environment Lively4 achieves a similar development experience, but targeting general HTML elements.
Web Components as a new Web standard provide a very powerful abstraction mechanism. Plain HTML elements provide direct building blocks for tools and applications. Unfortunately, Web Components miss proper capabilities to support run-time development.
To address this issue, we use object migration to provide immediate feedback when editing UI code.
The approach is evaluated by discussing known problems, resulting best practices and future work.