Yes you can, and you should! The included versioning is there for simplicity if you do not want the hassle to maintain your own git repo. But the real git will always be more powerful.
There is a github action to automatically deploy from github to windmill: https://github.com/windmill-labs/windmill-gh-action-deploy
That gh action is what I use myself for the public templates that hydrate every workspace on:
https://github.com/windmill-labs/windmill
Fun fact, the way it works is that it just tarball a subdir of your repo and send it as an input of a normal windmill script that then just extract it to your workspace (for all the diffs that it finds).
Note: It is still a one-man, early startup for now. I am looking for a technical co-founder and applying to YC. The stack is Rust, Svelte and Postgres :)
Note2: I am also looking for early customers and would be happy to customize windmill to your needs if you were to trust us.