I imagine that it was not quite so, and more akin to the more limited role we see in the American North, like Massachusetts or New York, but would love to learn a bit more!

Honestly? It was less significant in Canada than it was in the Northern United States. No ship carrying human cargo directly from Africa ever came to the colonies that are now Canada. This isn't to say Slavery didn't exist in Canada - thousands of Indigenous individuals were enslaved - but Canada had extraordinarily little to do with the Transatlantic Slave Trade when compared to the United States or other British possessions in the Western Hemisphere. Interestingly, though, slavery persisted in Canada significantly longer than it did in various parts of the Northern States.

According to Trudel, New France had 1,132 African Slaves in 1759. The Canadian Encyclopedia raises that estimate into the 1400s at the apparently-undefined "height of slavery" in the region and I'm inclined to take the larger number at face value. Before the American Revolution, the Nova Scotian census recorded 104 Black slaves in the colony, but that number rose roughly tenfold after the revolution as loyalists fled to Canada with their slaves - and Britain passed a law clarifying that loyalists who did so would retain their slave ownership, as a means of encouraging loyalists to move to Canada. Apparently about 2000 slaves were brought into the country at this time, with a little over half of them going to the Maritimes, 300 to Ontario, and 500 to Quebec. Oddly enough, about 3000 free Black Loyalists also moved to the Maritimes around this time, just under 1200 of whom would later leave and help settle Sierra Leone out of frustration at discrimination in Canada. Total numbers are pretty hard to find, but it's unlikely the territories that would later become Canada ever held more than a few thousand black slaves altogether at a time.

Anti-Slavery legislation began in Ontario in 1793, but unfortunately, it was much like the kind of Legislation New York would pass six years later and was more of a guarantee of the eventual end of the practice than anything - moreover, it was actually much more limited than its New York equivalent. There are records of slaves fleeing Canada to Free Territories in the United States, including New York, Vermont, and the Northwest Territories which would later become Michigan and Ohio. Various legal challenges attempting to neuter the institution arose in the late 1700s and early 1800s across the colonies, where in Nova Scotia it was ruled that the only way to legally reclaim a freed slave was to present comprehensive Proof of Ownership documentation that few slaveholders actually had - a ruling that set precedent across the Maritimes and was used as an argument in other provinces - and the Chief Justice of Lower Canada found that since Montreal didn't have the appropriate type of prison to hold fugitive slaves they could not legally be detained there and were thus free when the issue came to him - claiming that this ruling set precedent and applied to all future cases, though I am unable to find evidence of whether it actually worked beyond the specific cases he presided over. In short, Slavery kind of withered on the vine to the point where Ontario had less than 50 recorded slaves in it by the second decade of the 19th century, for about 40 years until it was eventually completely ended by an act of British Parliament in 1834. No part of what would become Canada actually passed a law granting freedom to all slaves within its boundaries at any point.

Surprisingly little actually exists talking about the role of slavery in Canada, but despite the relatively small numbers, it would be a mistake to assume that treatment of slaves in Canada was in any way better than it was in America. Almost no laws actually existed on the treatment of slaves, and it's safe to assume that life was not particularly pleasant. They were property with almost no protections under the law, and their expected lifespan was not particularly long.

Frankly, it's not as significant of a part of the Canadian national story as it is in America, despite being a horrifying part of our past, so it's rarely brought up or thought about. It was never the defining issue of an era or the backbone of the economy of any part of the country, and it eventually died with a whimper, not a bang. It's just a dark smudge on our record that I assume most (white) Canadians rarely think about and would prefer was forgotten.