Travel from Assisi to LaVerna

Unless you drive (rental car or private driver) to make it there and back in a day would be a major challenge.

The drive would be relatively short: freeway to Pieve Santo Stefano, then regular (albeit super curvy) highway to La Verna, so you can make it there easily in less than 2 hours (I've done it more than once).

By public transportation it's a major effort. You would need to take a train from Assisi to Arezzo, which is easy and fast, then at Arezzo you switch to the train that goes to Stia-Pratovecchio in the Casentino Valley. You would get off that commuter train at Bibbiena Stazione, where you'd take the H11 bus (Autolinee Toscane) to Chiusi della Verna (down the hill from the Sanctuary). The bus ride from Bibbiena to Chiusi della Verna is only 45 min. but my wife regularly gets car sick on that road when we drive there, so if you get car sick, be ready.

There might be also a bus that takes you to Pieve Santo Stefano, then another bus to La Verna from there. Haven't checked that option.

EDIT: the H11 bus goes across the pass from Valley to Valley. Basically from Bibbiena in the Casentino Valley to Pieve Santo Stefano in the Tiber Valley, passing through La Verna in between. So, besides the train to Bibbiena, then the H11 (or also the H12 bus) you could also take the H11 bus from Pieve Santo Stefano. There are no trains to Pieve Santo Stefano, but there is a bus from Perugia with the Sulga bus company.

If all planets align, you might make it there in less than 5 hours.

My personal take: Drive!!

Thank you Roberto. As I researched that is what I thought but was hoping I was wrong! I’m thinking rent a car for two days… will need to go to Perugia to do so I think.

If you go by car, then you might as well swing by Caprese Michelangelo to visit Michelangelo's birth house and eat at Il Rifugio restaurant. Website below:
https://www.ilrifugioristorante.eu/

Michelangelo was born in town here since his father was the Podestà (chief magistrate) appointed by the Medici family to that role in this area. The Michelangelo's family moved back to Florence when Michelangelo was still an infant.