Hi Bill!
This topic has been a long standing issue going back to 2012 or so (Optics Pro 8?), and I share your sentiments. There needs to be more granularity in settings for these parametric sliders - but I seriously doubt this will ever be done… after all its been six years - and we’ve got a DAM to build! 
There is a “Feature Request” along these lines that You could vote for here…
For those not familiar with Adobe’s approach… here’s how Photoshop does it (please see Fig.1 below): the markers, circled in magenta, can be moved to affect smaller or greater ranges for a given parametric segment - simple & effective…
Fig.1
