There will be a taxi rank at the station, but whether the taxis are regular I do not know. There is a big red notice on the Peschiera taxi website which implies to me that the number of taxis is insufficient to meet demand. It recommends using their mobile number if the fixed line doesn't work, and advises booking your taxi the day before in summer.
This will be an expensive ride. The taxi website does not give a fare to Malcesine, but gives 150€ to Riva whihc is not much further. https://www.taxipeschiera.it/wp/listino-prezzi/