Not shootings. Killings. Some of the worst mass killings in history didn't involve a gun. The Kyoto Animation arson is a great example. Higher death count than any mass shooting in US history except for two.
However, it's virtually impossible to find a list like this. I'm specifically thinking random attacks by one or two people, so things like war crimes don't count.
I'm sick of people declaring that mass killing only happens in America. The fact that trying to Google this inevitably leads you back to lists of US mass shootings - obviously on purpose - certainly doesn't help. I don't expect to change any minds using facts and data, but it makes them feel stupid and that makes me feel better.
There are images posted of US mass shooters (3 or more victims) that include gang shootings.
I don't know of any list for mass shootings worldwide, like OP is asking for. The organizations that might compose a list would probably be biased (intelligence, UN, NGOs)