Ah, here we are. I've decided to invent my own personal rules while writing! Here's one I adapted from something I vaguely remember learning about way back in high school.
If you have parentheses within parentheses what do you use? Brackets. And after that? I'll just demonstrate.
([{< >}])
If you need any more parentheses than that, consider restructuring your sentence.
Also take note: I'm not an editor or English professor or anything of the sort. I've simply started defining my own personal rules and decided to share them because it's after midnight and I have thrown all caution and logic right in the wind's face.
Extra Note: I suppose you could use asterisks inside of those chompy-things (angle brackets?) if you want, but those have other uses.