The OP made a big mistake in not investigating the ramifications of
having this garbage arrangement before purchasing the unit. If someone
casually told me that my car has to be moved so the trash from the
building can be picked up, I would certainly have investigated it
further and at the very least, had a written guarantee from the condo
assoc that it is their responsibility to move the car so the garbage
can be removed. Most likely, I would not have bought the unit, unless
it had some very unique features or price that justified it.

Now I agree with the advice to find a good real estate attorney. Make
sure they have experience in condominium law. If nothing in the Master
Deed or Bylaws says anything about your parking space being unique in
regard to having to move your car for trash removal, IMO, you are in a
very good position to prevail. Your deed gives you rights to a parking
space equal to all other owners and the condo association cannot impose
restrictions on you that limit your use and rights that do not apply to
others.

But here's the real problem. Though I think you have an excellent
chance of prevailing, this can be very costly. You have to pay your
legal fees, while the condo assoc will be represented by a lawyer paid
for by all the owners, not just the trustees. And many trustees would
rather waste lots of time and money fighting something like this,
rather than do what is right. If were you, I would first try to reason
with the trustees. Tell them you want to work with them to find an
alternate solution. It sounds like that is possible, since you
mentioned the trustees suggested you pay for the solution. I would try
to work with them on the basis of first figuring out what could be done
and avoid the issue of who should pay for it. Try to document as best
as possible what you get out of them from this process, as it will be
useful if you have to go to court. Ideally, what you want is
something in writing like: A shed of size X, could be put in location
Y, etc. That shows that there is clearly a reasonable alternate
solution. With that in hand, then you can negotiate who pays for it.
Even though you shouldn';t have to pay a cent, you could consider
paying something towards it, because otherwise you will spend a lot of
money on legal fees. Trustees have been known to take this kind of
thing to trial, appeal, etc, so it could cost you a lot.

I tend to doubt you have a claim against the seller, because they did
disclose this arrangement upfront.

Another long term approach would be to get elected as trustee, get
other sympathetic owners elected, etc. With a majority you could then
solve it the right way.