I implemented lsp-rename (new name is passed as a parameter) and lsp-rename-prompt (new name is prompted) commands in kak-lsp. But I must admit that I didn’t give it a good test, that’s why I put up a release candidate at https://github.com/ul/kak-lsp/releases/tag/v5.10.0-rc.1 and ask you to help me to ensure that feature works as expected.
Warning: renaming could go wild and eat your laundry, so better to commit your work before testing!
P. S. Not sure why Mac binaries are missing, I’ll try to fix it asap.