customize-jupyterlab

Use this skill whenever the user wants to change how JupyterLab or xtralab looks or behaves — hide or show sidebar tabs, change the default theme, disable extensions, hide the status bar, move the activity bar, register a language server, tweak CodeMirror or notebook defaults, customize the xtralab launcher or sidebar, change keyboard shortcuts, edit context or menu items, set per-user defaults that survive reinstalls. Also use it when the user wants to _add_ new UI or behavior — a toolbar button, status-bar item, sidebar panel, custom command, menu entry, launcher card, file handler, mime renderer, or any "ad-hoc extension" — since those need a labextension, not a config tweak. Use it even when the user does not say "JupyterLab" or "xtralab" explicitly, as long as the context is a Jupyter notebook environment or the xtralab desktop app. Teaches the four config surfaces (page_config.d, default_setting_overrides.d, jupyter_server_config.d, lab/user-settings) and the fifth surface for runtime behavior (share/jupyter/labextensions/), how to find them with jupyter --paths, and where to write changes safely without touching installed package files.

Compatibility

Requires JupyterLab 4+ and the `jupyter` CLI on PATH. Works with pip and conda installs, and with the xtralab desktop app (which sets `JUPYTER_CONFIG_DIR` to its own per-app directory).