It has something called "Custom Words" which might be what you are describing. Haven't tested this feature yet properly.

So is this already in Handy or you are referring to a feature of the underlying models you are still not actively using?

This is already in Handy in Advanced > Custom Words.

There is also Post Processing where you can rerun the output through an LLM and refine it, which is the closest to what Wispr Flow is doing.

This can be found in the debug menu in the GUI (Cmd + Shift + D).

I dig that some models have an ability to say how sure they are of words. Manually entering a bunch of special words is ok, but I want to be able to review the output and see what words the model was less sure of, so I can go find out what I might need to add.

There’s a PR for this which will be pulled in soon enough, I can kick off a build of the PR if you want to download a pre release version

Okay so it's more directly text replacements

https://github.com/cjpais/Handy/actions/runs/21025848728

There is also LLM post processing which can do this, and the built in dictionary feature