Advanced Edit Vol/pan/delay/fx Modify 'slider'

In Advanced Edit, then Vol/Pan/Delay/FX Modify, in addition to what’s already on there - Add, Sub, Mul etc., how about some sort of slider that makes adjustments in real-time, rather than specifying values and click Apply everytime make a change?

Sorry could someone move this to the main Ideas & Suggestions forum? Just realised I’m not query a 2.8-specific feature.