[vocaro]

I don't think this is possible in the current version of OmniFocus. I was also wanting notes to be visible all the time, but I couldn't find any way to do it.

It's strange, given that OmniOutliner makes notes always visible by default. One would think OmniFocus would work the same way.

I recommend submitting this as a feature request directly to OmniGroup using Help > Send Feedback.