I've very happily parked across from the V.Mestre station in a multi storey car park used by both visitors and residents. It tends to be somewhat less expensive (haven't checked this year's prices, nor those of Tronchetto) but you do need to get a Regionale train from V. Mestre to V.SL for a Euro or two each.
The drive to Venice from Verona is a busy Autostrada with tolls and, especially as you approach Venice, a solid wall of heavy goods lorries (tractor trailers) nose to tail making getting off at the right exit a little difficult. Lots of people do park cars for Venice because they all have to get out of the cars.
If you are going on to Salzburg you will be backtracking to Verona anyway. You can get very cheap fast train tickets from Verona to Venezia and you may be able to get parking in Verona quite easily and at a reasonable price. Can you leave your car where you will be staying in Verona and have free parking while in Venice?
For me, as the money could easily be the same or cheaper by planning ahead and taking the train, much less stress, and that fabulous breath taking experience of walking through the station, to the top of the wide broad steps down to the Grand Canal and being plunged immediately into the ambiance of true Venice - - well, I'd take the train.
Beats rocking up in a car park and walking across your first Venice piazza full of cars and buses.
BUT - you're not me and YMMV.