Indeed. I wrote an article a while back showing this in action with a Gamecube game running in an emulator: https://www.smokingonabike.com/2021/01/17/hacking-super-monk...

I remember doing this with the built-in tool of some emulator. They would let you filter by exact match and you could filter it down again after changing the value (losing a life).

But for stuff where exact matching wasn't practical like say a more or less continous health-bar, you could instead filter by searching for values that decreased / increased / didn't change.

Of course you would also have to guess at the data type but there weren't that many likely choices.

This is it. You'd mark the memory locations, go back to the game, repeat the search and filter down.

Either that, or you'd just go about trying one by one until you found it, then tried to figure out a pattern of what was around it and make notes on a paper for next time.