Just FWIW I'd say
for (1) yes it's perfectly OK to put the money in the folder, and just get up and leave. you're the heavily paying customer, you've paid and you're done. at a cafe that would be normal. maybe the staff will wave bye-bye to you. at a nice restaurant, the staff SHOULD come and fuss over you as you leave!
for (2) inside the book, just so it doesn't blow away
for (3) if you do not need change, screw them, do not wait. if you do need change, just wave and yell out to the waiter. put your hand up and say hello or some other word
Of course, it's completely normal in many parts of europe that people, simply, "hang around" a lot, are slow processing the payment at eateries, ie, it could take a long time for the guy to come back to make change.
If you're in a hurry to get change, it's utterly normal to (i) stand up and walk right over to either the cash machine, or a waiter, and give them the folder, to get your change. or indeed if you're in a hurry, here's a tip, (ii) AT THE MOMENT they drop off the folder, have your wallet out, and put in a bill. the waiter will then make change on the spot or go to the machine for the change
(or similarly have your credit card ready and the moment the folder arrives, give the folder back to the waiter, with, your credit card)
hope it helps!
ps you know how you mention, in Germany the waiter generally immediately collects the cash. I'd say, really it just varies all over (europe) - I don't think there's a particular flavour in one country or another. it's all pretty relaxed!