I think mental practice (e.g. visualizing yourself playing in the place you will perform next day, going through the sheet music consciously noting your intent

I think mental practice (e.g. visualizing yourself playing in the place you will perform next day, going through the sheet music consciously noting your intent and possible difficulties, or memorizing complex passages without the keyboard etc.) is a great complement to actual physical practice. It's no substitute, but at least it can be done basically anywhere.