Free access to Venice museums for the disabled, but with parking

Since your parking venue in Fusina is Parcheggio custodito 24h, you probably have a simple solution, at least to solve the Blue Badge problem. Make a photocopy of your Blue Badge, and take the original and the photocopy to the car park attendant. Since the car park is staffed 24 hours per day, you can ask them to check your original and then annotate the copy with their name and a message to indicate that the original has been checked.

In case you don’t speak Italian, I would suggest language such as “Ho bisogno di usare questo tesserino per accedere dei musei. Per favore puo mettere suo nome sulla copia e la lascio sul cruscotto?”. On the photocopy write something like: “Originale visto da Pinco Palino” and date and time. Pinco Palino would be replaced by the parking attendant’s name. Then leave the photo copy on the dashboard.

Proof of disability in Italy is a very precise requirement. For example for the Vatican

Free entry, without the need to wait in line, is granted to all
disabled visitors with certification of invalidity of 74% or over

Edit: This appears to be purely Vatican city rule and not aligned with Italian law stated below.

Needless to say, not too many foreign disabled visitors have a card with their percentage disability readily to hand.

The lack of a European-wide method to indicate disability was raised in parliament in 2013 regarding a proposal originating in 2011:

There are 83 million EU citizens with some kind of disability. They
are entitled to enjoy the right to freedom of movement, as recognised
by Article 26 of the Charter of Fundamental Rights of the European
Union, as much as non-disabled EU citizens. While in their home
countries there are a number of benefits in place for people with
disabilities, such as concessionary fares, which facilitate their
mobility and inclusion in all areas of social, economic and cultural
life. However, these benefits cannot be transferred when travelling to
another EU Member State, in order to work or go to university or for
other purposes. This is a serious obstacle to the full enjoyment of
the right of freedom of movement.

Which received the following answer (abbreviated):

The growing interest of EU Member States has enabled the Commission to
initiate a project working group where representatives of interested
Member States and civil society are dealing with practical details of
issuing and managing a European model disability card. This group is
still in the early stages of its work but the expectation is that the
card to be developed is likely to grant benefits in the areas of
culture, leisure, sport, transport and tourism.

In 2015 the following a “position paper” was published with the results so far:

incluD-ed asks the new EC, the European Parliament and EU MS to
establish an EU Mobility Card providing “mutual recognition of
disability status and thereby facilitating free movement of persons
with disabilities in the EU

i.e. not a great deal.

Italian law providing access for the disabled says:

Possono inoltre entrare gratuitamente nei luoghi espositivi alcune
categorie di persone tra cui:
…
i cittadini dell ‘Unione europea
portatori di handicap e ad un loro familiare o ad altro accompagnatore
che dimostri la propria appartenenza a servizi di assistenza
socio-sanitaria (Decreto Ministeriale n. 239 del 20 aprile 2006);

Which states essentially that free access sould be provided by law to the disabled and their assistants who can show they are eligible.

http://handylex.org expands on the precise requirements saying

Non è precisato quale documentazione sia necessaria per dimostrare la
propria invalidità, né – soprattutto – come si accerti l’appartenenza
a servizi di assistenza socio-sanitaria.

i.e. that the documentation required is not specified in the legislation.

In the absence of any precise requirement and any EU standard, the following anecdotes are offered:

http://boards.cruisecritic.co.uk/showthread.php?p=50053153

I travel a lot and visit lots of museums in the EU and have never
been refused disabled concessions ( including Rome). I take a copy of
my Blue Badge and DWP letter

I suspect the author is visibly disabled though.

https://www.euansguide.com/reviews/italy/lazio/rome/the-colosseum/review-this-is-how-is-could-be-done-nicola1972/

We were asked for proof of disability but had none (blue badge back in
England), but as my husband has a clearly visable physical disability
we were waved in to the shorter queue.

Free access to the vaporetto limited to wheelchair users:

Just tried it today. They won’t accept any disabilities unless you
have a wheelchair. (I live near Venice and work there).

http://boards.cruisecritic.com/showthread.php?t=2348207

Note: the Parking Badge is what was suggested to us by the ticket
booth at the Vatican Museum as being adequate proof.

Other people have suggested a doctor’s note, but I’m dubious about the value of a written letter.

In summary I suggest you use the method indicated at the beginning of this post to obtain the original Blue Badge to take with you. If you have any other official documentation, then obviously take that too.

This document may also be useful and provides links to the various Disability Benefits and Entitlements in European Countries

Buona fortuna!

I went to numerous museums in Venice (and Florence and Verona) last summer with a friend in a wheelchair, and she was never asked for documentation at any of them. Simply being in a wheelchair was proof enough.