I’m not at home with Renoise but I know I did something to bind my Lines slider to show and output values with no decimals, or at least I think I remember doing so. Maybe not to the full extent you want but it’s only a small tool so maybe have a look see if you can pull out something useful.
I have to say that GUI in general, especially syncing sliders, value boxes and parameters, has been my biggest struggle with the API so far.