An extension that might meet this need is jupyterlab-fonts.
After pip or conda installing, it enables somes menu items, command palette items, and a sidebar for customizing font family, font size, line height, etc.
Alternately, you can customize it through the settings UI, but probably only via the old-fashioned JSON settings editor, as it hasn’t been updated to work with the form-based one.
However they are edited, the settings are stored in your jupyter application directory that persists between launches, and can be deployed in e.g. Binder with overrides.json.