We wasted half the day in Amsterdam, searching for a place where we could leave the boat "just for some hours". Apparently it just wasn't possible, though eventually we found a place where we could pay a reasonable price for an overnight stay
There is one spot in Oslo with a train station and many work places, quite expensive to park cars there, but up until recently it was possible to leave the boat there totally for free - I often did that, left the boat there in the morning and took the train to work - but sadly now someone has put up lots of signs "private quay no mooring". I can understand it, because eventually there were several ships there moored permanently that looked like they could sink any moment; some of them even damaging the quay due to waves and bad seamanship.
it would be hard if it's a boat
you really have to have permit to get to park
it's a busy canal out there
no one's just allowed to park
but maybe somewhere in the Schaanse Zaans you could have had a chance for a free parking though am not so sure about it