There are no direct night trains connecting either of those pairs.

No night trains operate from Spain. The closest you can get is to go by high speed train Madrid - Barcelona and then “Local” train (taking several hours) to either Cerbere or Latour De Carol across the border in France where night trains with seats and couchettes but no sleepers run to Paris.

Berlin - Venice there are several route options, you can get a night train from Munich to Venice or a night train Berlin - Vienna.

That makes sense. 

I just checked and l cannot seem to even book one from Munich to Venice. 

I've been on the OBB website multiple times and other websites and have not been given an option to choose a type of accommodation for sleeping. I feel like I'm missing something!

Thank you for helping me.

Possible connection from Berlin to Venice: 17.34 by ICE from Berlin Hbf to Augsburg Hbf, Nightjet to Venice leaves 23.02 (Nighttrain does start in Stuttgart at 20.29, go there if you'd like to enter the night train earlier, e.g. if booking a sleeper, but that would mean to leave Berlin much earlier).

Book it here: https://shop.oebbtickets.at/en/ticket?cref=oebb-allgemein

But you need to book the day train and the night train seperatly.

To book a train from Berlin to Augsburg or Stuttgart, choose "Seat reservation only". This reservation is not mandatory. 

To book the night train from Stuttgart or Augsburg to Venice, choose Eurail as discount and then "One-way tickets and day tickets". This reservation is mandatory. 

Of course you need to check what's available for your given date. The Nightjet has seating, couchette and sleeper carriages. 

Here’s a good map of Nightjet and Eurocity. It covers the vast majority of night trains in Germany and Austria. 

https://www.nightjet.com/en/dam/jcr:6a8041cb-0131-4ad3-84fd-25154548e5dd/nightjet-streckennetz-deutsch.pdf

And some good information about the sleepers from Cerbere or Latour De Carol to Paris. It’s written as a London-Paris-Barcelona (and return) journey, but it’s just as useful for you for Barcelona-Paris.

https://www.seat61.com/Spain.htm#london-to-barcelona-by-train

Have you found the train you want but can’t reserve, or are you not even seeing it in the search results?

As above, you need to add the Interrail/ Eurail discount where it says ‘Adult’, and then search for ‘one-way tickets and day tickets’. On Nightjets, this should give you the option to see sleeping accommodation.

There are some dates where the train doesn’t run due to construction work, and other dates it might be full, but this is what you should see if there’s availability. (I chose a date at random)

Thank you so much! Thats greatly appreciated.

How does the global pass work online for these night trains? Its saying the cost is €200. 

If that's for one person, then that's probably a normal fare, not a pass reservation.

On tickets.oebb.at, add the Interrail/Eurail discount and then select "One-way tickets and day tickets”. (Do not use "Seat reservation only”.)

Thank you so much! I finally got it!