I installed a git precommit hook and sometimes I want to commit with --no-verify flag. I know how to do that in command line but I'd like to do that in TortoiseGit (since command line is very poor in Windows). How can I do that? I read through https://tortoisegit.org/docs/tortoisegit/tgit-dug-commit.html but can't find anything helpful.
No, it's not possible right now (as of 2.13.0.0) - it's not documented explicitly, just deducible using the source code.
If you use TortoiseGit, you should consider to use TortoiseGit hooks instead of vanilla git hooks.