GTK per programme styling - synaptic

[shufei]

I have set some preferences in ~/.config/gtk* for my ease of use on a tablet. But some programmes are not obeying this. Synaptic, for one, stubbornly maintains a razor thin scrollbar (slider). I’d like to widen this. How can I set gtk styling css for recalcitrant windows? I’ve found very little help for this issue thus far.

Thanks!