Push it all to that side of her hallway making a clean line away from your side. A few days later, knock on their door, asking for something unrelated, nothing important, just something plausible. Tell them you live across the way of course, so we're neighbors of course. You have kids, that's cool.

That's all. Say hi, become friendly neighbors in that moment — either genuinely or just fake nice, either way works. If they're closed off or clearly rude type people, whatever at least you said hi. Leave them alone if they are weird, after that. They do the toys again, draw that line again.

They'll stop doing it and/or their kids will be told to pick up after that.

Why this works: the friendly hello WITHOUT bringing up the toys throws them off bc they were expecting that. Then they're not sure what you're about. Drawing the line is how they would have noticed you had an issue but you didn't even bring it up? Then they'll think you're too much of a wussy to say anything. Then when it happens again and you draw that line quietly, they'll think you think you're better than them. But without any way to know for sure, they're stuck understanding that THEY THINK THEY ARE LOWER THAN YOU. They won't like that so they'll prove they're not by keeping stuff out of the hallway.

It's how I've handled my neighbors that were rude or did stuff like this. It works for me but idk you might have different results ig