I'm pretty sure the older Firefox debugger had both of your easier tools, and the new one probably does too. "Stack and step collapser" was called "blackboxing"

I'm pretty sure the older Firefox debugger had both of your easier tools, and the new one probably does too. "Stack and step collapser" was called "blackboxing". "Stack of stacks", also known as long stacks or async stacks, is definitely implemented at the lower levels (at least for non-primitive exceptions); I'm not sure whether or how they were surfaced in the UI.