That rule will not have the proper effect in the upcoming major JupyterLab: https://github.com/plotly/plotly.py/blob/92ce5bce770dc5390bda0f44a9b6b033d4f2c39e/packages/javascript/jupyterlab-plotly/style/index.css#L26 You should set `height` directly. See https://github.com/jupyterlab/jupyterlab/issues/13227 for more details.