Hello zhani
To enter Switzerland:
As a general rule:
You need valid travel documents if you want to travel to another country. If you are a passport holder of a nation that does not require a Schengen Visa, you can travel.
If you are a passport holder of a nation that does require a Schengen Visa, you either need a Schengen Visa or a valid resident permit of a participating Schengen country.
With an expired resident permit your entry might be denied. Imigration controls are also conducted on border crossing trains.
I suggest to check your case with the Swiss Embassy in Italy:
https://www.eda.admin.ch/countries/italy/it/home/rappresentanze/ambasciata-roma.html
To reenter Italy:
Here is a website that says, you can reenter, but be careful if you trust information from unverified sources:
https://www.meltingpot.org/2023/01/uscita-e-rientro-in-italia-in-attesa-del-permesso-di-soggiorno/
Best to clarify with the immigration office in Italy which is in charge to renew your resident permit.
Kind regards,
Roland