@jupyter-widgets/jupyterlab-manager extension which satisfies this requirement.
When using ipywidgets 7.6 or newer in JupyterLab 3.0 or newer you do not need to do anything: it is installed by default. You can check if this is installed by running:
jupyter labextension list
which should include a line like:
@jupyter-widgets/jupyterlab-manager v3.0.0 enabled OK (python, jupyterlab_widgets)
jupyter labextension install @jupyter-widgets/jupyterlab-manager