Trill line without tr symbol (code review needed)

I would like to have trill ine without tr symbol.
As my first patch in the project, I've created an implementation in https://github.com/briff/MuseScore/commits/pure_trill_line
If you were so kind to review it, I would be happy to finalize that.
It looks like this:

There are questions:
- do we need to have a separate icon in the toolbar for this type?
- what should be the name (if "pure line" is not appropriate)?
- any other thing to fix? Or better do this with any - optional - symbol?

Thank you,

Bertalan