At the edge of this concept lies not the actual end of everything, but the edge of human ability to comprehend. What is a thing? Are there aspects of thing-hood that we can reason about?
Is Harry Potter a thing? Does Absolute Everything include Harry Potter? Does it include all possible but not actual things? I’m going to eat fish for lunch today, is the possibility that I could eat pizza part of Absolute Everything?
To shorten this, concepts have to fit inside our brains and so there lies your bigger concept than Absolute Everything. To get meta on the concept of concepts and drive out new categories involving your meta-theories.
For example, concepts compress information. So you might imagine a class of concept that can’t be compressed, and so can’t be included in the concept of Absolute Everything.
Did I actually find something outside of Absolute Everything in this answer? Probably not. But this is one of those things where the musing is more important than the answer.