I suspect this is related to this answer.
However, since you are already using ipywidgets, I wonder if there are other ways to achieve something like you want to do without adding in ipylab yet. You can have ipywidgets need something interacted with before it continues to do what it next does when it observes an appropriate change. I wonder if that sort of direction may be compatible with what you need here as it works with more modern Jupyter use.