There is a TLA+ formatter available here: https://github.com/FedericoPonzi/tlaplus-formatter
The formatter is still work in progress. It uses the official SANY implementation from tlatools. It's open for contributions as well, if you have experience in crafting formatters or compilers please do reach out.
The plan is to integrate it to vscode-tlaplus: https://github.com/tlaplus/vscode-tlaplus/pull/327