Sonar can do that, if I understand your question correctly.
- First thing, select the clip by clicking on it, and it will highlight. Make sure to select the clip itself. You don't need to select the track first.
- Then go over to the Inspector and select the "Clip" tab.
- The top item in the Properties field is "Clip Name", which will of course correspond to whichever clip you selected. I don't know if there is a character limit - I haven't encountered one in my use.
- Just type whatever you want that slot (to the right of "Clip Name") and it will show up on the little bar atop the selected clip.
Hope that solves it!!