Another interesting tool is ProB[1]. I believe it does symbolic model checking and supports partial order reduction. It works on specifications in multiple languages, including TLA+, but I haven't had the chance to use it myself because it doesn't support all TLA+ features. In particular, it doesn't support TLA+'s higher-order operators, which my specifications use.
Appreciate the reference. I'm holding off on ProB and B for now because the B method has mixed results in CompSci literature. I mean, it's been proven on a number of high assurance projects by pro's. I at least like that both B and TLA+ are pretty straight-forward to compared to most where a person has both a mathematical and good, mental model of what's going on. B particularly as it maps to imperative with ease.
I'm keeping it bookmarked just in case. Meanwhile, I just got a ton of stuff on asynchronous verification in response to another commenter's troubles there. I was away too long: looks like async and GALS are both mostly solved problems at the cutting edge with some tools to help. A lot to skim or read that puts my B experiments further on the backlog.
[1]: Cool visualizations: https://www3.hhu.de/stups/prob/index.php/State_space_visuali...