I often use the ÖBB map of sleeper services - which covers their own trains and some Euronight services, but notably misses SNCF and Trenitalia.
I was searching online for a more comprehensive map, and found this - an interactive map of all the sleepers in Europe, including details on frequency, timing, operator. It’s a great piece of work.
I’m sure it will be a useful resource. Apologies if already posted somewhere.