Complex sentence: The party is currently active, but has lost importance as most of its leading members, including Roberto Visentin, Pietro Fontanini, Sergio Cecotti and Alessandra Guerra, left to form Lega Nord Friuli since 1990.
Split into simpler sentences: The party is currently active, but has lost importance. Most of its leading members, including Roberto Visentin, Pietro Fontanini, and Sergio Cecotti left to form Lega Nord Friuli since 1990.